Before you travel to the USA please make sure your ESTA is still valid.

Please log in and review your ESTA status in advance of travel, especially if you have not travelled since before COVID, you may automatically think your ESTA is still valid. 

I've had a a reader this week comment that they got to their airport and were told their ESTA has expired. If you get to the airport and log online to purchase an ESTA there's no guarantee it will be processed in time for your flight, don't make this mistake, check well in advance. Go to https://esta.cbp.dhs.gov/ and check the status of your ESTA in advance of your journey.