Is it permissible to combine the Maghrib and Isha prayers with a delayed combination (jam' ta'kheer) upon returning from travel, given the difficulty in performing Maghrib immediately upon arrival, and does the ruling differ if one eats before reaching home?

If the airport is outside the town, you may combine and shorten prayers there because you have not yet reached your hometown. However, if it is within the town, the ruling of travel ceases upon reaching it, and you should pray Maghrib immediately, without combining it with Isha, unless there is a need or hardship.