Handling fees.
Whilst the lo-cost carriers have opened up travelling by air as an option previously unavailable to many people, there are losers as well as winners.
In the mid-seventies, my parents took my sister and I on holiday to Lanzarote. It was the first time I'd travelled on an airliner. When I got back to school, it transpired that I was the only child in a class of thirty kids to have ever flown abroad. How times have changed. The prestige of travelling by air is a dim and distant memory. Now anyone can fly to Nice and back cheaper than going on the train from London to Birmingham.
I just wanted to put in my tuppence worth to this forum. Sooner or later the bubble is going to burst. I think the whole lo-cost 'concept' is unsustainable. Handling agents are already being squeezed, and the less money there is coming in, the less there is to be spent on providing a decent service. It is a usual sight to see a lone stressed out PSA checking in an entire A320 on their own. The passengers rarely complain though, as they know the score.
'...Sorry you've had to wait so long to check-in Sir, but you'll find a national carrier in the North Terminal who will gladly check you in in half the time, but charge you twice as much...'
The cost to the consumer of travelling by air is now way out of balance to realistic operational costs. Not just to handlers, but to every service provider involved in the business of getting the aircraft from point to point.
In summary, I'd like to play devil's advocate by suggesting that, travelling by air ought not to be 'the god given right' to every, thug, dole scrounger, and student. The airlines need to work together to steadily increase the air-fares to an acceptable commercial level, so that we can all benefit including, ultimately, the consumer. A cartel would bring back some level of self-respect to the industry.