Reminds me that when Greta Thunberg was investigating means of getting across the Atlantic, one way or other, an airline apparently suggested they could fly her over in a plane fuelled with bio(jet)fuel. They were already geared up to use a small percentage mix of the bio-derived, routinely. They couldn't actually do 100% bio, though, so they suggested a special 50% mix on both legs of a return flight, instead, which "adds up to 100%"(!).
Which further reminds me that, in times BCE (Before Corona Epidemic), there was a lot of fuss about flight/travel taxation geared up to allow "one flight a year", per person, before introducing punitive environmental taxes on further extravagances. As a sop to the then-current trend[1] for even the lowest of the lower-classes (especially them?) to jet off to somewhere with a beach and sun[2], they didn't want to make the first flight expensive, as there'd be a revolution, just make the Simon Cowells of the world pay more, not those who were more distant cousins of Joey Essex, as the closest they got to such a true jet-set lifestyle.
But they never said "return flights", which I thoroughly enjoyed the mental image of[3]. Chavvy McChavface and family could afford to go to Costa Del Smallchange, but would not be able to afford to fly back until the next calendar year. Or they'd have to revert to a continental ferry/etc for one of the legs.
[1] Not entirely beaten out of us, CE (Coronavirus Era), given the number of people who snuck in a sneaky holiday to Croatia/etc then had to rush back before a certain desdline when it was announced that their destination was added to the Mandatory Quarantine On Return list.
[2] Usually as the UK enjoys "Hotter than Corfu/Morocco/The Bahamas" weather, here at home, or so the newspaper headlines tend to say a lit these last few years...
[3] Myself oonly ever been on one 'holiday' airplane (return-)trip, in a school outing to ski in the alps for a week or so. Every other visit to the continent (not on company business, and with no intention of just broiling myself mahogany-brown on a beach), including another one to the alps, was ferry/Chunnel and then road. And all but one of those that were family ones we only took the bikes across and cycled the whole rest of the journey in the country(/ies) concerned. Yeah, that's right... I was a Hipster before it was considered cool to be one!