JetBlue AirwaysIn anticipation of increased Covid-19 infection among flight attendants and pilots, the airline is slashing nearly 1,300 flights from Thursday to mid-January.

JetBlue, a New York-based carrier, and others including United Airlines, Delta Air LinesAnd American AirlinesThey have cancelled over 4,000 flights in the last 24 hours, citing bad weather and increased sick calls.

In a Tuesday note to employees, three JetBlue leaders stated that the past week had been “one of our most difficult operating times during the pandemic.” The note was read by CNBC. “The rapid growth of Omicron cases in just a few days is something that nobody could possibly prepare for,”

The airline said it would cancel its flights to “get even further ahead” of Omicron’s expected rise in cases. JetBlue plans to reduce flight schedules by slightly less than 10%.

JetBlue cancelled 104 flights on Wednesday, which is 10% of the airline’s schedule.

Monday, the Centers for Disease Control and Prevention cut its recommended isolation timeFor individuals who tested positive but are not yet symptomatic, the maximum time for treatment is five days.

JetBlue was following Delta in last week’s flight urging the CDC to halve its guidanceFor breakthrough Covid cases, isolation should be limited to 5 days. This is in warning of staff shortages and flight disruptions. Others airlines followed suit.

JetBlue’s leave policies were updated to accommodate staff who are symptom-free within five days of the CDC announcement.

In the staff note, the airline heads stated that they were hopeful that new guidelines will help speed up staff return. However, they added that Omicron cases had not reached their peak in the Northeast for at least two weeks and that it would take longer.