Vilnius or Kaunas - which is cheaper to fly from?
Lithuania's two big airports are a hundred kilometres apart and travellers genuinely choose between them. We price both, so here is what the fares say, route by route, rather than what the airlines would like you to assume.
Vilnius and Kaunas sit about a hundred kilometres apart, a bus or a drive of ninety minutes or so between them, and for a lot of Lithuania either one is a realistic option. The low-cost carriers have split them: Ryanair built an early base at Kaunas and flies a lot from it, Wizz Air leans on Vilnius, and both airports reach most of central Europe. So the sensible question before booking is not which airport is nicer - they are much the same - but which one is actually cheaper to the place you want to go.
The honest answer is that it depends on the route, and not randomly. On the cheapest, most-flown hops the two airports are a dead heat, because the same airline flies the same aircraft to the same city from both and prices it the same. They differ on the less contested routes, where the airline based at one airport flies a route often while the other barely serves it. Below are two routes that show both directions of that, priced from each airport, so you can see the gap yourself.
Where Vilnius wins - Dublin
Same airline, same season, and Vilnius is cheaper than Kaunas in every month we can compare.
Dublin is flown from both airports by the same carrier, on much the same calendar, which makes it a clean test: strip out the airline, the aircraft and the season, and what is left is the airport. Priced side by side, Vilnius is cheaper in every month the two share, and the gap holds all year rather than appearing once. It is not a large amount of money, but it always runs the same way. This is the more common pattern across the routes both airports fly: where neither carrier is pushing the route especially hard, Vilnius tends to be slightly cheaper, and it flies to more places besides.
Priced from Vilnius, month by month.
The same route from Kaunas, on the same months, for the comparison.
Where Kaunas wins - Malaga
On the Spanish sun routes the result flips, and Kaunas is the cheaper airport.
Now take a winter-sun route. Malaga is where Kaunas wins: its based airline flies the route often through the cool half of the year and prices it below Vilnius for the months it operates. The two charts below are not the same length, and that is itself part of the answer: Kaunas flies Malaga as a seasonal winter route and prices it low, while Vilnius spreads a thinner service across more of the year. If your Malaga trip falls in those winter months, fly from Kaunas, and the Malaga guide covers why those are the months to want anyway.
Priced from Kaunas, month by month.
The same route from Vilnius, for the comparison.
Beyond the fare
The two airports are not interchangeable on the ground, and for most people that matters more than a few euro.
Vilnius airport sits about six kilometres from the city centre, a few minutes on the airport shuttle train or a short bus ride, so for anyone starting in Vilnius the transfer takes minutes. Kaunas airport is out at Karmelava, roughly fourteen kilometres northeast of Kaunas and a bus of half an hour or so from that city - but a hundred kilometres and the better part of two hours from Vilnius by coach. That distance is the whole decision for a lot of travellers. If you live in or near Vilnius, the time and cost of getting to Kaunas usually wipes out any fare saving and then some; if you are nearer Kaunas, the reverse is true and the drive to Vilnius is the thing to price, not just the ticket.
The airports themselves are much the same for a short trip - small, low-cost, quick through security outside the peak departure waves. Neither has a lounge worth planning around and both are easy. So the tie-breaker, once the fares are close, is almost always geography and timetable: which airport you reach with less driving and fewer changes, and which one has a departure at an hour that does not cost you a night's sleep or a taxi at each end.
So which airport
Put the two together and the rule of thumb is this. For the rock-bottom central-European hops - Kraków, Milan, Gdańsk - the two airports tie, so there is no fare reason to prefer one and you should pick on the ground: whichever airport you can reach with less driving, fewer changes and a better departure time. Across the wider map Vilnius edges it more often than not and flies to more places, so as a blind default it is the safer bet. But it is not a clean sweep, and the Spanish sun is the clearest exception, so check your actual route rather than trusting a reputation.
If breadth rather than a single route is what you are after, the cheapest flights from Vilnius rank the whole map from one airport by the floor we have measured on each one, and the same logic works from Kaunas. And whichever airport you pick, the month you fly moves the price more than the airport does, which is the argument we made on one route across a full year.