United Airlines this week announced that, beginning March 23, it will begin accepting credit and debit cards for onboard purchases within North America, South America and the Caribbean. United will phase out cash acceptance next month except on international flights, where it will continue to accept credit and debit cards and cash. Cash will continue to be the only payment option on United Express flights. In addition, JPMorgan Chase & Co.'s United Mileage Plus Visa cardholders will earn 10 miles per dollar they spend on in-flight purchases. Travelers approved for a Mileage Plus Visa card using an application distributed on certain flights also will earn 30,000 Mileage Plus points and $25 off their next United Airlines ticket. Separately, AMR Corp.'s American Airlines earlier this month announced it will accept only major credit and debit cards for onboard purchases beginning this summer.