Plot hole: Near the end of the film Drax tells Bond he had his own shuttle hijacked because he needed it after another shuttle malfunctioned. OK then why didn't Drax just contact whoever he needed to before the Moonraker left on the 747 and have the working shuttle returned to his base before it left. He obviously had the time to get two of his people hidden in the shuttle so a few phone calls would have fixed his problem and the British government would have never had to involve Bond at all.
Plot hole: For the shuttle to land at Drax's Amazon hideout he would need a very long runway, something that could easily be detected by satellite.
Suggested correction: Why would they need to have their own runway? With everybody else dead, they could just pick from any existing landing sites. Also, it is not clear if they planned to use the shuttles for the initial return at all. Apparently, the pods at the end of the spokes are constructed with independent reentry capability, or else how would Bond's comment about the chances of Jaws and his girlfriend make any sense.
Suggested correction: No reason the Amazon crew couldn't construct one once the gas has dispersed, and everyone else on Earth is dead.
Plot hole: After the six shuttles take off, there are obviously dozens, if not hundreds of Drax' minions left behind in the base. Not regular employees, but the kind that knows what's coming, if only because Drax is obviously talking about it, e.g. to Bond, quite openly. Would they just stoically stay behind to be gassed? One would think they would mutiny and rush the shuttles wouldn't one?
Suggested correction: No reason they couldn't have been brainwashed into obeying Drax like here was a god. Further, for all we know, the base could have secure facilities for the employees, who have been sterilized, doubtlessly, to wait until the gas in the atmosphere has dispersed sufficiently. Drax needs ground personnel to enable people to land on Earth later on.
If you have gas-tight bunkers on earth, the whole exercise of taking everybody to orbit would be a bit pointless, wouldn't it?
But Drax has a god complex: he wants to stay in his "untainted cradle of the heavens", instead of the planetary surface. Not to mention, just in case something goes wrong with the Amazon bunker, his master race will be safe and secure in the orbit.
Plot hole: The British government sends its best agent to the headquarters responsible for a missing shuttle, and Drax immediately wants to kill the man sent to talk to him. Surely Drax would have been smart enough to know if he had Bond killed both the American and British governments would have investigated him, even if he could chalk up Bond's death as an accident.
Suggested correction: So the villain not killing Bond is a mistake, the villain killing Bond is a mistake too? Like in all spy movies, killing the best agent would win Drax a lot of time to further his plan and eliminate evidence, even if the American and British government will investigate. With Bond dead and the government unable to prove anything for now, Drax is surely not worse off than with a very curious and suspicious agent searching through his hideout now and finding out possibly even more.
Plot hole: It would be impossible for Drax to decontaminate the laboratory and remove the equipment in Venice and return it to the room we see in the amount of time given.