Cancellations are catching many travelers off-guard as Americans return home after the holidays, with thousands of flights being canceled in the days after the Christmas holiday.

Travelers were subjected to lengthy delays, successive cancellations, and repeatedly rescheduled flights as they struggled to get back home. Flights across the country were disrupted by a wide range of factors coming together at once.

Due to heavy snowfall, flights in Seattle were canceled throughout the weekend and into Monday. Other flights were delayed due to delayed flight crews or rescheduled due to a shortage of flight crews. One flight returned to Seattle after Delta Airlines (DAL  ) reportedly found Chinese sanitation protocols "not operationally viable."

Individually, many airlines have suffered similar disruptions on and off throughout 2021. In August, Spirit Airlines (SAVE  ) experienced a wave of cancellations amid weather and staffing shortages. Southwest Airlines (LUV  ) suffered a wave of cancellations and delays in October, with Southwest's pilot's union suggesting the company's mismanagement compounded with staffing shortages.

Alaska Air (ALK  ) was one of the hardest airlines hit in the recent wave of cancellations, finding many of its Seattle flights scrubbed due to weather and Omicron variant-related staff shortages. The story was much the same for SkyWest (SKYW  ), which found itself canceling hundreds of flights over the weekend.

The ripple effects that disrupted holiday air travel are likely to reoccur, given the ongoing prominence of the coronavirus and a growing shortage of pilots. Limited relief may come in the short term, however.

On Monday, the U.S. Centers for Disease Control and Prevention (CDC) revised guidance for post-infection isolation, reducing the recommended time to five days from ten. While this is posed to help staffing in the long term, the weather is expected to remain particularly hazardous in the short term, likely prolonging many weather-related delays.