asked the Minister for Aviation Supply what further developments are being undertaken to improve on the performance of the Harrier vertical-take-off aircraft.

During the next two years the Pegasus engines at present installed in the R.A.F.'s Harriers will be replaced by more powerful versions. We are also studying the feasibility of a further up-rating of the engine, but no decision has been made to proceed beyond this study.

Will the right hon. Gentleman bear in mind that there is a large requirement by the United States Navy for the Harrier if its payload and range are increased? Will he give the maximum priority to the development of the proposed Rolls-Royce Pegasus engine, because that would probably achieve that result?

Yes, Sir. We are aware of those facts.

Can my right hon. Friend say what anti-pollutant arguments the United States Government are putting up about the Harrier, in view of the fact that they have just purchased it for their own use?

I am not immediately aware of those arguments, but I shall look into them and write to my hon. Friend.