DALLAS (AP) -- Spirit Airlines Inc. is expanding again at Dallas-Fort Worth International Airport, where the dominant carrier, American Airlines, is in bankruptcy protection.

Spirit launched its first international flight from Dallas on Thursday with daily nonstop service to Toluca airport outside Mexico City.

The Miramar, Fla.-based airline also began daily nonstops between Dallas and Detroit, San Diego and Portland, Ore. The airline offered a two-day fare sale on some tickets to promote the flights.

Spirit arrived at DFW Airport in May 2011 and has expanded to 15 destinations. The low-fare airline has said its expansion at DFW is unrelated to American's problems. American and parent AMR Corp. filed for bankruptcy protection in November.

Spirit shares fell 18 cents to $20.30 in midday trading.