The flights are the main expense that await travelers when they want to take a trip, for this reason I have found links that might be useful and save some Euro.
Skyscanner
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A good site where you can find and compare prices of different companies.
Lastminute
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A good site where you can find and compare prices of different companies, there is the possibility give dates of variables to find the best price if you party a few days before or after.
Momondo
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A good site where you can find and compare prices of different companies, there is the possibility graphically to see if there are better prices around the dates we requested.
Which Budget
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On this page you can find good information of the possibility to travel with airlines low-cost,
select the location of departure and arrival will show ...' the low-cost airlines that are running
that way.
Backpackers Travel
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A travel agent where you can find great opportunities flight.
Zingarate
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All flight companies Low Cost updated daily.
Liligo
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Excellent search engine to find a flight at the best price.
Airline Route Maps
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A site where you can see all the air routes of the various companies in the world.
SeatGuru
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Interesting site where you can view a map of the seats aircraft of all companies.
Flightradar24
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A beautiful site where you can see the routes of aircraft in real time and a lot of information of each flight.