Also, when looking for flights remember the aeroplane!

What I mean is that you don’t want to end up on a short haul aircraft on a long haul flight. If you look at flights to BKK from LON you will find Qatar, Finnair (BA about to resume direct service but not yet) and combinations usually of BA with Qatar or Royal Jordanian. Alas, if you choose the BA/Royal Jordanian combination then your flight between LON and Amman will be on a BA narrow bodied aircraft with only economy type seats. Club Europe may be fine for a quick hop but it’s miles and miles to Amman!

With the examples I gave Finnair use narrow body on the LON to Helsinki stage, but some daily flights are long haul wide body aircraft. But this is a short hop.
All the others are wide bodied.