The airline industry has been the major bright spot of the market, but has all the easy money been made? These lesser known airlines are where you will find the biggest share price gains in the industry going in to 2015. Act now before the rest of the market wises up and the rally begins. 

The airline industry has been the best performing in the market over the last three months, up 30%. And over the last year, it is up 58%.

Hands down, the airline industry has been the best place to be invested over the last few years thanks to various mergers that have led to industry consolidation. The recent fall in oil prices has really helped bring the industry into focus.

It's no secret that fuel costs are the largest expense for airline operators. About a third of an airline's' entire cost is usually fuel. And with oil flirting with $50 a barrel, this could be the catalyst that helps make 2015 another stellar year for the high-fliers.

And there's a lot working in the favor of airlines; the combination of lower fuel prices and the right-sizing of the industry are the two well-known catalysts.

As well, rising employment and the strengthening economy will be big positives for airlines. More money in the pockets of consumers and businesses are positives for airline travel. Flying is becoming easier and more convenient, with airlines offering Wi-Fi, installing outlets and offering more leg room.

But everyone loves to talk about the major airlines, including United Continental (NYSE: UAL), Delta Air Lines (NYSE: DAL) and American Airlines (NASDAQ: AAL).

However, with the stock price of all three up more than 40% over the last three months, I'd expect investors looking to play the bustling airline industry to focus more on the under-followed names.

This comes as not all airlines have enjoyed the same upside as the jumbo airlines. With that, here are the three most underrated airlines for 2015:

Underrated Airline For 2015 No. 1: Alaska Air Group (NYSE: ALK)