The schemes, to increase the airports' capacity, are the first to fall victim to a review of spending on airport construction.
Andrew Wolstenholme, BAA's group construction director, confirmed that the projects, designed to increase the number of passengers that can embark and disembark, have been deferred. The Pier 6 contract at Gatwick, worth £90m, was due to be completed in 2003.
The decision will hit framework contractors including Mansell, Warings, Mace and Llewellyn.
Wolstenholme said: "Pier 6 has not been cancelled - it has been deferred. At the
moment we are manufacturing some of the sub-assemblies; we're putting it in the position where we can proceed [in future]."
The Pier 6 project would have involved constructing a passenger bridge across a runway, and the creation of "docking stations" at the end of the bridge.
The project at Heathrow is Victor Pier at Terminal 4. The contract is worth tens of millions.
We’re trying to address the effects of 11 September
Andrew Wolstenholme, BAA executive
BAA's spending at Heathrow, originally planned to be £230m this year, will probably fall to £210m. Wolstenholme described this as a "pretty minor dip".
Wolstenholme added that BAA intended to spend at least £300m next year. He said:
"There is no huge dip [in our construction spend]. If you look at the numbers we are still on a huge cost investment programme. It is about projects that address short-term capacity. We are trying to address the effects of 11 September. It's quite certain there is going to be a short-term blip."
He said some minor projects would be brought forward, such as a programme of work to separate incoming and outgoing passengers, and that these would compensate for the reduction in large projects at the two airports.
Framework contractors said they were working closely with BAA over the cutbacks.
Andrew Gay, non-executive chairman of contractor Warings, said: "Obviously the downturn in flight passengers is having an effect. BAA is postponing projects that can be put off for a while."