I understand that the Rules of the Air were derived mostly from international maritime law, where many of the issues had been resolved. In ships/boats, you keep right as you pass: "When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision each shall alter her course to starboard so that each shall pass on the port side of the other". (Note - overtaking seems to be be different - it is simply necessary to keep clear, if there is room either way). Why UK chose left for roads is more the mystery - though as UK invented it for roads first, the rest of the world should have followed. Napoleon, however, decided differently for France, no doubt USA rebelled against the former colonial rulers in principle, and so it went on. I was told that the rule of the road (UK) was actually based on keeping the horseman's sword hand free to defend against somebody coming the other way, but that might be apocryphal.
Re roads and the sea - A. P Herbert, lawyer, author and playwright of humorous inclination, wrote a series of "misleading cases" pointing up anomalies in the law. His fictional character, Mr. Haddock, was accused of colliding in his boat with a car. His defence was that rowing up the River Thames, he kept right, as he should according to maritime law. The river had flooded over the road at Richmond (?). Along the road, travelling through the flood waters, was the injured party in his car, keeping, as he should on a road, to the left. Hence the collision.
So what does a hovercraft do when moving from water to land? Is it a ship, an aircraft or a land vehicle for legal purposes?
What should vehicles do airside at aerodromes, when meeting a taxying aircraft?
Chris N.