Read the contract, guys. They can do it as long as they meet certain requirements for compensation.

In my 8 years I've seen them do it a couple of times. I've also seen them offer to buy back vacations voluntarily several times.

 

Yes it is valid, it's in the contract that you've been working under for the last year and half. Here are the relevant sections...


The Company may not cancel a pilot’s vacation. If Company
operations necessitate the postponement of vacations, the
Company will first solicit volunteers for such postponement. If
there are insufficient volunteers for such postponement, the
Company may make such postponements mandatory. The
Company will give at least fifteen (15) days notice of vacation
postponement.
2. Voluntary postponements will be awarded in seniority order.
Involuntary postpone-ments will be awarded in inverse
seniority order.
3. A pilot whose vacation is postponed pursuant to paragraph
C.1., above, may select a non-postponable vacation from
open vacation for the current year or may add such vacation
as non-postponable vacation to the ensuing year’s usable
vacation. After such vacation has been awarded, a pilot will
designate which period(s) will be non-postponable. A pilot will
have the option of receiving vacation pay in lieu of reschedul-
ing a postponed vacation period.
4. When scheduled vacation dates are involuntarily postponed
by the Company, the Company will reimburse the pilot for all
non-refundable deposits made by the pilot in reliance upon
the originally scheduled dates. The Company must be
expeditiously advised by the pilot that postponement of a
scheduled vacation will result in a forfeiture of a deposit. The
pilot will be reimbursed within thirty (30) days of submitting
appropriate documentation of the forfeited deposits. The pilot
will use his best efforts to assist the Company in the recovery
of the deposit.