Actually, the US, the UK and France had contracts with the Soviets that guaranteed them access to Berlin by air. They didn't have correspnding contracts for access via streets and railways, though, that's why the Soviets could block food trucks but not the airlift.
The contracts only allowed very specific air corridors (3, to be precise), which is one of the points why the airlift was so hard to implement at full capacity.
The Allied forces had quite extensive rights in all the other sectors, and not just in Berlin. For example, military vehicles were considered extraterritorial, and had to be let in. And that's what the US and the UK did: they drove into East Germany and rather openly spied on Soviet troop movements and maneuvers.
The contracts only allowed very specific air corridors (3, to be precise), which is one of the points why the airlift was so hard to implement at full capacity.
The Allied forces had quite extensive rights in all the other sectors, and not just in Berlin. For example, military vehicles were considered extraterritorial, and had to be let in. And that's what the US and the UK did: they drove into East Germany and rather openly spied on Soviet troop movements and maneuvers.