Alaska Airlines today became the nation's third airline to eliminate cash purchases on all of its flights. Beginning next month, the airline will accept only debit and credit cards for onboard purchases of meals, drinks and in-flight entertainment. Southwest Airlines may be next. A spokesperson for Southwest tells CardLine the airline is testing credit card-only purchases on some flights, and this fall it expects to make an announcement regarding a new systemwide cashless policy. Virgin America has accepted credit cards and declined cash on its flights since its launch nearly a year ago. Several airlines, including Delta Air Lines and American Airlines, began testing cashless flights last year, and in November JetBlue Airways Corp. eliminated cash (CardLine, 11/28/07). United Airlines and U.S. Airways each say they are testing cashless flights. Toronto-based Guestlogix Inc., which is involved in several airlines' tests of in-flight card acceptance, provides Alaska with the hand-held card readers flight attendants use to accept payments. Alaska Airlines says for a limited time it will sell $5 vouchers at its ticket counters to pay for onboard purchases for passengers who do not have credit or debit cards. To promote the new cashless policy, Alaska Airlines passengers who use the Alaska Airlines Visa card will earn 10 miles for every dollar they spend onboard through Oct. 31.