The most common mistake is assuming any calm bay qualifies as a landing site. In Indonesia, a seaplane base is treated as an airport and must be certified or registered under CASR Part 139 Volume III (Keputusan Direktur Jenderal Perhubungan Udara Nomor KP 206 Tahun 2021), with adequate depth, a proper taxi channel, and shoreline facilities — not just still water.
Why Do Charter Requests Keep Naming Spots That Aren’t Actually Sites?
Clients often pick a bay off a satellite map because it looks flat and sheltered. Flat water is not the standard. Indonesia’s Directorate General of Civil Aviation (DGCA), part of the Ministry of Transportation, adopted seaplane-base standards derived from FAA Advisory Circular 150/5395-1 and published them domestically as the Manual of Standard CASR Part 139 Volume III, Seaplane Bases (Waterbases). Under CASR sub-regulation 139.101, a water aerodrome must be certified or registered the same way a land airport is, and the shoreline facilities that support loading, mooring and passenger transfer fall under that same certification chain.
KP 206 Tahun 2021 goes further and sets the minimum technical and operational specifications for water aerodromes used by seaplanes carrying up to 30 seats. That means a site is either on the approved list, in the process of registration, or it is not a legal option for a commercial charter — regardless of how it photographs.
What Changed With the August 2025 Regulation?
A ministerial regulation enacted 22 August 2025 (State Gazette 2025 No. 620) formally defines an “aerodrome water” as the water area used for seaplane arrivals, departures and surface movement. It requires seaplane operations on water to follow shipping-sector law as well as aviation law, and it obliges water aerodrome organisers to coordinate directly with coastal radio stations and Vessel Traffic Service (VTS) units before and during operations. This closes a gap that used to leave water landings governed almost entirely by aviation rules while ignoring the maritime traffic sharing the same water.
Which Mistakes Actually Sink a Site Proposal?
Most rejected or reworked site requests trace back to a short list of recurring errors. The table below groups the seven that come up most often when a client, agent, or production coordinator proposes a location directly, along with the fix a licensed operator applies before flight planning proceeds.
| Mistake | Why it fails | The fix |
|---|---|---|
| Treating an uncertified bay as usable | Only sites certified/registered under CASR 139 Vol. III (139.101) count as legal water aerodromes | Cross-check the site against DGCA’s registered base list before it enters any itinerary |
| Ignoring tide state at the planned time | Preferred depth is 1.8 m; below the 1 m single-engine minimum at low tide, the aircraft cannot safely operate | Plan around a tide table for the exact charter date and hour, not a seasonal average |
| Sitting too close to a reef edge | Reef proximity restricts the safe landing and taxi run and raises grounding risk | Confirm the taxi channel — at least 45 m wide — has clear water on both sides, oriented into prevailing wind or current |
| Overlooking shipping lanes and vessel traffic | CASR Part 91 requires the aircraft to keep clear of vessels and follow right-of-way rules on the water | Coordinate with the relevant coastal radio station and VTS unit, as required under the 22 August 2025 regulation |
| Skipping village or local consent | A site can be technically compliant and still be operationally unworkable without community agreement | Confirm consent and any local access terms as part of the same pre-flight site check, not as an afterthought |
| No alternate site named | Weather, tide, or vessel congestion can close the primary site with no notice | Every charter plan should carry a named, equally compliant alternate before departure |
| Wrong payload assumption for a hot day | Density altitude on a hot, still day shortens the safe takeoff run and reduces usable payload | Confirm passenger and baggage load against the day’s actual conditions, not a brochure capacity figure |
Three of those seven — the uncertified site, the skipped village consent, and the missing alternate — account for the bulk of last-minute charter changes reported by coordination desks working across multiple islands. None of them show up on a satellite photo.
The stakes multiply on a longer itinerary. A client planning a remote island seaplane charter across several water aerodromes in one day needs every stop checked against this same list, not just the first one — a multi-leg route amplifies any single site’s weaknesses across the whole day.
How Do Depth, Tide and Channel Width Actually Get Checked?
Depth is the first filter. DGCA’s base standards call for a preferred water depth of 1.8 metres, with 1 metre treated as the adequate minimum for single-engine operations. That number is not fixed everywhere: the water operating area length is increased by 7 percent for every 300 metres of elevation above sea level, which matters for highland lakes and crater-lake sites considered for scenic or charter use.
The taxi channel — the stretch of water an aircraft uses to move between the landing run and the shoreline facility — needs to be at least 45 metres wide, with direct access to onshore infrastructure and, where possible, oriented into the prevailing wind or current. A channel that is technically deep enough but too narrow, or oriented across the current instead of into it, still fails a pre-flight check even though the depth reading looks fine.
Why Does Vessel Traffic Belong on the Same Checklist as Depth?
A water landing site sits inside water that boats, fishing fleets and sometimes commercial shipping already use. CASR Part 91 treats the seaplane the way it treats any vessel on the water: it must keep clear of other traffic and follow right-of-way rules rather than assuming priority because it is an aircraft. This is exactly what the August 2025 regulation formalised — water aerodrome organisers now have a standing obligation to coordinate with coastal radio stations and VTS units, not just file a flight plan and go. A site with heavy daily fishing traffic or a working anchorage nearby needs that coordination built into the schedule, every time, not negotiated on the day.
Why Does Village Consent Belong on the Checklist, Not Just the Chart?
A site can clear every technical box — depth, channel width, certification status — and still be the wrong choice if the nearby community has not agreed to regular aircraft movement, mooring, or passenger transfer through their waters. This is not a regulatory line item in CASR Part 139, but it is a practical one: an uncooperative shoreline turns a compliant site into an unworkable one on the day of the charter. Coordination desks that skip this step tend to find out about the problem at the worst possible time — with passengers already airborne.
What About the Day a Site Looks Fine but the Conditions Aren’t?
CASR Part 91 also sets equipment thresholds tied to distance from shore. No take-off is permitted for a flight over water more than 50 nautical miles from shore without a life preserver or approved flotation device for every occupant. No flight beyond 30 minutes or 100 nautical miles from shore is permitted without specified survival equipment, including life preservers fitted with locator lights. These thresholds apply regardless of how calm the water looks at the chosen site, and they are a licensed Part 135 operator’s responsibility to confirm before departure, not something a client checklist substitutes for.
Payload is the other condition that quietly changes day to day. A hot, still afternoon shortens the safe takeoff distance available and can reduce how much weight the aircraft can carry off the water safely, even at a fully compliant site. A desk that only checks capacity against a brochure figure, rather than the specific day’s conditions, is one of the seven recurring mistakes in the table above.
What Should You Ask a Charter Desk Before Agreeing on a Site?
A short set of direct questions, asked before a site is locked into an itinerary, filters out most of the problems above. The table below lists the ones worth asking every time.
| Question to ask | What it confirms |
|---|---|
| Is this site certified or registered under CASR Part 139 Vol. III? | The site is a legal water aerodrome, not an informal location |
| What is the tide state at our planned arrival time, not just today? | Depth will meet the 1 m minimum (1.8 m preferred) at the actual hour of landing |
| What is the taxi channel width and its orientation to wind and current? | The channel meets the 45 m minimum and is usable on the planned day |
| Has VTS or the coastal radio station been notified for this route? | Coordination required under the 22 August 2025 regulation is in place |
| Is there a named alternate site if this one is unusable on the day? | The charter has a fallback rather than a cancelled leg |
| Has local community consent been confirmed for this specific site? | The landing will not run into an on-the-ground access dispute |
| How does payload change if conditions are hot and still that day? | Passenger and baggage limits reflect real density-altitude conditions, not a brochure number |
A desk that answers all seven without hesitation is working from a compliance file, not a guess. A desk that cannot answer the tide or VTS questions specifically for the requested date is still working from a general assumption about the location, which is the same assumption that causes the mistakes above.
Frequently Asked Questions
Who decides whether a water landing site in Indonesia is approved?
Approval sits with Indonesia’s Directorate General of Civil Aviation (DGCA) under the Ministry of Transportation. A site becomes an approved water aerodrome once it is certified or registered under CASR Part 139 Volume III sub-regulation 139.101, following the technical specifications set out in KP 206 Tahun 2021. A charter desk does not approve sites; it confirms a site’s existing registration status before including it in an itinerary.
Can a private client request a new, unlisted landing location for a charter?
A location can be proposed, but it cannot be used commercially until it meets CASR Part 139 Volume III certification or registration requirements, including depth, taxi channel width and shoreline facility standards. Getting an unlisted site added to the approved list is a regulatory process handled through DGCA, not something a single charter booking can shortcut.
Does the site-approval process differ for a scenic flight versus a multi-day island charter?
The certification requirement does not change — every water aerodrome used commercially must meet the same CASR Part 139 Vol. III standard regardless of trip purpose. What changes is exposure: a multi-day or multi-stop itinerary touches more sites, so tide, VTS coordination and payload conditions need checking at each stop, not once — which is why coordination desks treat a multi-leg charter as a longer checklist, not a bigger risk.