Thousands of holiday air travelers who anticipated heading back to work Wednesday were instead stuck in airports across the country on Christmas Day after United Airlines cancelled hundreds of flights for a second straight day due to a weekend snowstorm that hammered its Chicago hub.

By midday Tuesday, United, the nation's No. 2 carrier, had cancelled nearly 250 flights, or close to 20 percent of its total flights globally, according to FlightStats.com. This came after the Chicago-based carrier wiped nearly 150 flights off its board on Monday following a winter storm that paralyzed Chicago's O'Hare International Airport on Sunday.

By cancelling flights Sunday and Monday, many of United's flight crews and planes were not in position to keep Tuesday's schedule.

United decided to cancel 244 flights on Tuesday, hoping to get its schedule back on track for Wednesday's expected heavy passenger load, spokeswoman Robin Urbanski told the Chicago Tribune.

"We did proactively cancel flights today in order to best accommodate customers and get them to their destinations," Urbanski told the newspaper.

Click here to read the Chicago Tribune story.

American Airlines, United's main competitor out of the Chicago O'Hare hub, cancelled about 40 flights Tuesday.

Sources told the Tribune that United's lean staffing contributed to the decision to cancel flights.

United cut back on the number of pilots it employs in hopes of improving the carrier's bottom line, but the move also left the carrier open to deployment shortages caused by foul weather.

Complicating matters for United: it had to find volunteers to fly its planes on Christmas Eve and Christmas day, when many pilots were reluctant to leave their families for work, the Tribune reported.