Thousands of flights within the United States and internationally were delayed and hundreds were canceled early on New Year’s Eve, adding to the tally of delays and cancellations during the holiday week due to adverse weather conditions and rising cases of the Omicron coronavirus variant. Over 2,400 flights were canceled globally as of early Friday, including over 1,100 flights within the United States or entering or departing it, according to a running tally on flight-tracking website FlightAware.com. There were nearly 4,000 global flight delays in total. The Christmas holidays are typically a peak time for air travel, but the rapid spread of the highly transmissible Omicron variant has led to a sharp increase in Covid-19 infections, forcing airlines to cancel flights as pilots and crew need to be quarantined. The sudden arrival of Omicron has brought record-setting case counts to countries around the world. Transportation agencies across the United States are suspending or reducing service due to Covid-19 staff shortages as the Omicron variant surges nationwide. On Thursday, for the second day in a row, the United States had a record number of new reported cases based on the seven-day average, with more than 290,000 new infections reported each day, a Reuters tally showed, as US officials weigh the impact of the Omicron variant. US airline cabin crew, pilots and support staff are reluctant to work overtime during the holiday travel season despite offers of hefty financial incentives. Many workers fear contracting Covid-19 and do not welcome the prospect of dealing with unruly passengers, some airline unions have said. In the months preceding the holidays, airlines were wooing employees to ensure solid staffing, after furloughing or laying off thousands over the last 18 months as the pandemic crippled the industry.