Fear of catching the C-19 virus itself is not the only thing holding back air travel. Most people cannot take the risk of being ordered to self-isolate at short-notice upon their return home (or at intended destination). People are wary following the debacle of the on / off 'travel corridors' and are in no hurry to be caught out by these again. Many lost money on non-refundable items like car hire and accommodation in 2020; they don't want to lose more. Others are put off by the requirement for a covid test taken within 72 hours of departure, often at greater expense than the underlying air fare. For a family that cost can mount up, and the test is only good for one trip. Some jurisdictions aren't allowing overseas nationals in at all yet, and we can't predict when that will change. Other countries have more overbearing restrictions than others: anyone fancy being muzzled-up 24/7 whenever outdoors in a tropical climate? And then there is the admin factor. Few relish another round of interminable phonecalls listening to muzak, unanswered emails and long waits for travel vouchers when flight arrangements have been cancelled yet again. Or - in the case of some Ryanair routes - customers lost their fares as the airline went ahead with flights which the passenger as an individual was banned from using on the grounds of nationality / residency.
My travel for the first half of 2021 will be limited to very late bookings with high confidence of going ahead to destinations which I know will be welcoming, open and not oppressively restricted. And I'll need to know that the destination I'm planning to visit isn't completely shut down too - we've got to be able to do the things we want to do and meet the people we want to meet when away. Avoiding the virus itself is only the start of it.
Set against this there are some positives. People holding travel vouchers will want to deploy them - especially if expiry date becomes an issue - though I think most of Ryanair's revert to a cash refund upon reaching their anniversary anyway. Though voucher redemptions don't represent new income for the airline. Folks who have worked throughout the crisis - in many cases (key workers) doing all the overtime they can bear - have the funds and inclination to treat themselves to a decent break away somewhere. Many of those furloughed have had money coming in and much reduced opportunity to spend. Pensions have been coming in as normal too. So there is pent-up demand to be satisfied once travel reliably opens up again.
When mass-market travel does come back, I would expect Ryanair to be a big winner. Their services can be booked easily at short notice to destinations which have been reliably opened up to visitors. They go to the right places for shorter, high confidence breaks away. And if travel is disrupted again, the funds committed are generally much lower than those for alternative long-haul or high-end trips. Ryanair also has the flexibility to blitz short-haul destinations which do reliably open up for bookings. Familiar 'old favourite' destinations will be in high demand once re-opened.