Bianca Carrasco has not seen her hard-shell purple Samsonite suitcase since she checked it at the Boston airport on Dec. 23.

Her connecting flight on Southwest Airlines from Denver to El Paso was one of more than 15,000 cancellations for the carrier in a holiday week meltdown that started with a monster winter storm and cascaded into days of travel chaos.

Family members drove 10 hours from El Paso to pick her up at the Denver airport so they could spend Christmas together. Even now that she’s back in Boston, the whereabouts of the luggage remain a mystery.

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Southwest’s policy allowing passengers a pair of free checked bags likely contributed to the pileup of missing luggage, travel industry experts say.

“There’s no question that Southwest handles more bags every day than other domestic carriers, since there is no financial incentive for passengers to cram everything into carry-ons with Southwest,” William J. McGee, senior fellow for aviation at the American Economic Liberties Project, said in an email. “Undoubtedly this contributed to the baggage fiasco last week.”

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