When I start planning a trip on of the first things I do it go to Kayak.com and see how much the flights are going to cost me. If I’m going somewhere EasyJet and Ryanair will take me I see what they run too. But baseline is Kayak, and apparently with good reason.

Lifehacker had a post profiling their top five user recommended flight search engines. They were:

1. Kayak
2. Yapta
3. Live Search Farecast
4. Priceline
5. Sidestep

I’d never heard of Yapta or Sidestep, so I went ahead and ran a little comparison of all the five sites to see which one gave me the cheapest flights. Of course I know that each of them will perform differently for different flights, but I wasn’t worried about being scientific here, I just wanted to see in a random sample which was best. And Kayak won, hands down.

Here are the results for the cheapest round trip from London to Nairobi later this month:

1. Kayak – $547.47
2. Priceline – $574.28
3. Sidestep – $627
4. Farecast- $657
5. Yapta – $713.51

Of course some of these searches offer other services. But the service I’m interested in the cheapest flight, so Kayak wins. Farecast claims to predict whether the tickets will get cheaper in the future, but only works in the US. Sidestep has a small price predictor, but it’s the exact same as Kayak’s – except all the flights are more expensive. So I’ll just stick with the one the gives me the cheapest flights.

I’d heard some rumors about Ryanair starting to run flights from NY to London, but this weekend brought even more news: they’ll be going from multiple US cities to multiple European cities.

Of course I’m excited for this news. I like Ryanair. I like that I get a cheaper flight if I don’t check a bag, check-in online, and can tolerate an airplane that has all non-advertising weight trimmed. But the news that they are spreading brings a nagging thought to me that they are turning into the Wal Mart of the skies – which would suck. Are they going to drive down quality and worker’s compensation and rights across the board?

I have enough traveler guilt knowing how much damage flying does to the environment. Do I also need to start worrying about flying an airline that will drive mom and pop carriers out of business and degrade the quality of air travel in general?