AVIATION officials have begun discreet talks with district board members to strike a deal which would result in an extra hour of flights at night in and out of Kai Tak. The Civil Aviation Department (CAD) wants to extend the use of the airport until 1 am, an hour later than the present curfew. With Kai Tak now operating at saturation point, an extension into the midnight to 6.30 am hours where there are no scheduled flights is the only way to further maximise its use. A CAD spokesman yesterday confirmed the talks had taken place, but would not say which boards or which members had been involved. ''There is no formal intention by the department [to extend flights beyond midnight] but there are informal exchanges of views to gauge the opinion of district board members,'' he said. He said the hour extension would be traded for a guarantee which promised that certain periods at night would be flight free. Under the present arrangement, flights after 9.30 pm are limited to 18 per hour. After midnight, only aircraft forced to use the airport for emergencies or technical reasons, such as unforeseen delays at other airports, are allowed to land. CAD would guarantee residents over both Kowloon and the Lei Yue Mun gap, absolute quiet periods at night, possibly between 3 am and 5 am, when aircraft could only land in an emergency. But any encroachment past the already sensitive midnight deadline is likely to cause concern to the 250,000 Kowloon residents living under Kai Tak's flight path. Kowloon City District Board chairman Wong Sik-kong said the board had not formally discussed the deal. But he added: ''All Kowloon residents are against [flights after midnight] but it is inevitable due to economic reasons. ''If it does ever happen the Government must take action to ensure environmental issues are addressed.'' Eastern District Board chairman Shum Choi-sang said he would consult the other members of the board on the issue. The board's Environmental Improvement Committee chairman Wong Chi-keung also said he would be opposed to any such deal. ''If the Government wants to do this they must show strong evidence that the economic reasons outweigh the environmental ones. ''Once they have done that, we can sit down and talk about it. But it should be remembered that even if the economic reasons are strong, there are a lot of people affected by noise.'' Legislator James To Kun-sun, who represents the Kowloon area, said he felt the Government was trying to pick off district board members in advance of putting forward solid proposals. ''This is what the Government has been after for some time and it doesn't surprise me that they have been talking to district board members. ''If they want to relax the restriction then they should consult the public. ''The deal is a rotten one, it is like me giving you a dollar and you giving me 90 cents back.'' Mr To tried unsuccessfully in Legco last month to force the CAD to set an upper ceiling of 22 flights per hour from 9.30 pm to midnight. Instead, the department gave an undertaking it would not increase flights above that limit.