They were unwilling, or unable, to guarantee safe passage from the city to the aircraft. [+ from/to]

他们不愿意或者不能够保证从市内到飞机场的安全通行。

We try to negotiate a safe passage for relief convoys which will travel that stretch of road.

我们试图通过谈判为将要经过那段路的救援车队争取到安全通行权。