I often have to fly on business trips, but the company doesn't always cover expensive tickets.

In that case, Lowcost Club is just perfect. There you can track the cheapest flights even to popular business destinations. Plus, the site allows you to subscribe to notifications about price reductions on the route you need. I used this service several times when I had to fly to Berlin urgently — instead of the standard price of 200 euros, I got a ticket for 90. It really helps to save money, especially if you fly often and your company has a limited budget for business trips.