A national pilots' organisation backed seaplane pilot Gerald Repacholi in his dispute with the Swan River Trust over plans to operate a sightseeing and water taxi service from Bull Creek on the Canning River.

The 17,000-member Aircraft Operators and Pilots Association said it would support Repacholi's efforts to continue the service. National director Tony Mitchell argued there was no legal reason a seaplane should be prevented from landing on the river in an open limit zone and described the Trust's action as an infringement of civil liberty.

Repacholi and fellow pilot Bill Russell planned to use Bull Creek as a base for sightseeing flights and a water taxi service. However, Swan River Trust chairman Geoff Totterdell issued Repacholi with a notice on February 6 effectively preventing him from landing on or taking off from the Swan and Canning rivers.

Trust manager Darryl Miller said the pilots could take off again but could not return without permission. He said the notice would not prejudice future applications to use the river.

Repacholi engaged lawyers to negotiate with the Trust and said he was prepared to take the matter to court if necessary. He maintained that he was operating within the law and had been issued a mooring by the Department of Transport the previous December.

The Swan River Trust said legal advice found that using the river for seaplane operations represented a material change of use within its management area, regardless of whether the service was commercial, and therefore required approval under the Swan River Trust Act 1988.

The proposal also faced concerns about safety and congestion. Aquatic Council chairman and WA Water Ski Association secretary John Wilson said the Canning River was already heavily used by skiers, rowers and sailors and argued that landing a small aircraft among other river users would be dangerous.