Occasionally it might may make sense to use a discount airline to fly to a nearby country and take a train the rest of the way. One example of this is to fly Lithuanian Airlines to Vilnius and take a train to Belarus, one the most expesive destinations to fly to in Europe.
http://www.myair.com/
Airline
Home Country
Air Lingus
Republic of Ireland
Air Berlin
Germany
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Latvia
Adria Airways
Slovenia
Agean Airlines
Greece
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Finnland
Blue Air
Romania
BMI Baby
UK
Centralwings
Poland
Click Air
Spain
Condor
Germany
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Turkey
Easy Jet
UK
Estonian Air
Estonia
FlyBe
UK
FlyGlobeSpan
Scotland
FlyNordic
Scandinavia
German Wings
Germany
Helvetic
Switzerland
Iceland Express
Iceland
Lithuanian Airlines
Lithuania
jet2
UK
Estonian Air
Estonia
Martin Air
Netherland
Meridiana
Italy
Monarch
UK
My Air
Italy
Niki
Austria
Norwegian
Norway
Onur Air
Turkey
Ryan Air
Ireland
Sky Europe
Eastern Europe
Smartwings
Czech Republic
Spanair
Spain
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Scandinavia
Sun Express
Turkey
Thomsonfly
UK
Transavia
Netherlands
Vueling
Spain
Virgin Express
Belgium
Wizzair
Poland and Hungary
Wind-Jet
Italy