Can pilots (of united i.e.) have their "mileage plus" card and therefore collect miles, while they are flying?

Question

Can pilots (of united i.e.) have their "mileage plus" card and therefore collect miles, while they are flying?

Answer 1

No... Pilots, flight crew members cannot receive miles for their working flights.  

Most frequent flier programs grant miles for only when the fare is purchased.  Pilots do however get flight hours to bank in their "experience" bucket which can used for promotions, new jobs etc.

Answer 2

Only for flights they pay for as a passenger.  But they get some number of free flights as a benefit anyway.