16600 pilots today
Add another 200 to finish out 2023
Add another 15000 (2500/yr for six years, also assumes none of those pilots hit retirement age before 2030)
Subtract 3450 retiring through 2029 (age 67 drops that number to 2050)
----------
28400 pilots
Of course, no one really thinks this hiring rate will continue for another half dozen years...