Plot hole: When Angelo sets the Vulcan down in the sea, he blows the canopy and extends the landing gear. As the plane settles, he attempts to release his harness, then has his air line cut by Largo. He futilely beats on the harness release, when all he had to do was pull the face curtain handles to trigger the ejection seat, which would not only blow him clear of the plane, but would separate him from the seat itself. Having trained for two years, for this specific mission, he would undoubtedly be familiar with ejection procedures.
Plot hole: Before the race starts, Sir Percy intends to sabotage some of the other fliers. He announces to Courtney that he had lured Dubois away by giving him the address of Courtney's daughter, but later, when the race starts, there is nothing wrong with Dubois' machine even though Sir Percy had the chance.