Well, they'd qualify for flight pay
If they're still on active duty and paid by the military services, then they would get their base pay for rank and years in service, food allowance, housing allowance, variable housing allowance (adjusted for cost of living in different communities), and flight pay. Flight pay may only apply if they're rated pilots but is a pretty substancial amount of money. Even non-pilots who perform flight duties are eligible for extra pay. BTW: the housing and food allowances are tax free. Astronauts travel quite a bit so they'd also be eligible for TDY (temporary duty) expenses and per diem.