Is it obligatory to perform Fajr prayer on the bus before its time expires, or to make it up upon arrival, knowing that the route is approximately in the direction of the Qiblah, and is it permissible to perform it sitting when there is no place to stand?

If a traveler begins his journey before Fajr, he must pray Fajr on the road before its time expires. If it is possible to pray standing outside the bus, that is obligatory. Otherwise, he should pray inside the bus, standing, facing the Qiblah, bowing, and prostrating. If standing is not possible, he should pray sitting, gesturing for bowing and prostration, making his prostration lower. If facing the Qiblah is not possible, he should pray in any direction.