Airlines just can’t get the world flying again. Despite a U.S. boom in vaccinations, many countries are battling a resurgent coronavirus. That means carriers are now expected to end 2021 offering about two-thirds the number of seats they did in 2019 and passenger demand could be even lower.

Globally, scheduled capacity is stuck at about 58% of pre-pandemic levels, says John Grant, chief analyst at aviation data specialist OAG. For every market that grows, another seems to fall back, he said.

Using weekly OAG updates, Bloomberg has built a global flight tracker to monitor the pulse of the air travel comeback.