a three-day rule before and the cdc compressed this time line because of the concerns over the omicron variant. airlines say they are going to comply with this but they're really pushing back on the efficacy of all this. this is what united airlines ceo scott kirby told me. >> the reality is omicron is already out of south africa. it's already escaped, on every continent. covid is unique. covid is indemic. we need to learn to live with it but we're not going to learn to live with it locking down and shutting borders. the right answer is to get everyone vaccinated. >> reporter: remember this applies to foreign nationals and u.s. citizens, regardless of vaccination status. one other big change here also going into effect, the transportation-wide mask mandate, a federal rule. it was set to expire on january 18th, 2022, now it's been extended two months. the new expiration date march 18th, 2022 and it applies on all