The phrase "airstrip in a" is not complete and lacks context, but it is grammatically correct and can be used in written English.
You can use it when referring to a specific airstrip that is located within a certain area or context, though additional information is needed for clarity.
Example: "The pilot was instructed to land on the airstrip in a remote part of the island."
Alternatives: "airstrip located in a" or "airstrip situated in a".
Close by, they were laying an airstrip in a recently made clearing in the forest.
We opted to stay in the mainly residential area near the airstrip in a quirky, three-storey house called Sandcastle.
After three hours, we landed at a dirt airstrip in a field of tall grass and taller termite mounds.
We left the airstrip in a string of vans and cars and drove along rocky, ascending roads toward a village called Mafeteng.
The day ends at Baadaran at the end of a 1950s airstrip in a remote pine clifftop cabin with an en suite shower.
Soon its wheels kiss a spit of an airstrip in a western Alaska place where senators and governors rarely visit, a Yup'ik Eskimo village called Akiachak.
I leave early next morning, jolting up to the airstrip-in-a-field where my tiny plane awaits.
If it took, say, demolishing a lakefront airstrip in an authoritarian fit, at least his has been a city that works, that sets and achieves an ambitious agenda (his).
As they arrived at Camp Rhino from its rough airstrip in an ambulance, the two less seriously injured marines -- one with his left hand wrapped in bandages, the other with an intravenous bottle attached to his arm -- were met by dozens of their comrades, who stood shoulder to shoulder, forming a cordon into the warehouse where doctors treated the two.
At this point, Commander Minoru Yano, who had arrived with the Japanese reinforcements on 29 August, took over from Hayashi, and after the survivors of the attack had reformed in the dead ground around Poin Creek, he led them about 200 yards north of the airstrip in an attempt to outflank the 61st Infantry Battalion's positions on Stephen's Ridge.
As the war progressed, the Japanese decided to build an airstrip in Sandakan, a small city on the northeastern tip of the island.
