Until Rapid Rewards 2.0, WN rewarded frequency only, not spending. If you did it right with the right promos, you could get a free ticket on WN redeemable for the last seat on a plane after flying four extremely cheap roundtrips. WN for years was the leader in rewarding frequency, not revenue from RR members. (Even without promos you'd earn a roundtrip after 16 one-ways or 8 roundtrips, no matter how cheap or short.) WN's lack of bankruptcy filings has a lot to do with fuel hedging, employee relations, smaller network, one type in the fleet, etc. more so than its FF program. (The change to the revenue-based RR 2.0 there has not been greeted all that warmly, as evidenced by the overall tone on the WN board.)