WASHINGTON, Dec 27 (Reuters) - Skyrocketing COVID-19 cases hobbled U.S. airline staff on Monday, causing hundreds of flight cancellations, and prompted the country's top infectious disease expert to suggest the government consider a vaccine mandate for domestic air travel.

Monday's travel woes capped a glum Christmas weekend for thousands of stranded passengers waiting in airport queues and on customer service phone lines to re-book flights, often days after originally planned.

Like other businesses, airlines have struggled with staffing issues in recent days, as the spread of infections from the Omicron variant kept pilots, cabin crew and other workers who have fallen ill at home in quarantine.

Bad weather has also taken a toll on travel. A total 1,148 flights into, within or out of the United States were canceled by Monday afternoon, according to the flight tracking website flightaware.com.

The average number of new COVID-19 cases in the United States has risen 55% to over 205,000 per day over the last seven days, according to a Reuters tally.

Anthony Fauci, the nation's top U.S. infectious disease expert, on Monday recommended the federal government consider a vaccine mandate for domestic air travel.

"That is just another one of the requirements that I think is reasonable to consider," Fauci told MSNBC in an interview.

U.S. President Joe Biden, speaking to reporters on Monday, declined to say whether he endorsed a vaccine mandate for domestic air travel.

He did say he was open to reducing quarantine times for other Americans after the Centers for Disease Control and Prevention (CDC) last week said healthcare workers could isolate for seven instead of 10 days.

In another instance of Omicron-induced travel misery, the CDC said on Monday it was investigating 68 cruise ships after reports of COVID-19 cases on board.