The F-35 Lightning II is a multi-role fighter jet under development in a joint project between the U.S. and many of its allies around the world. Built to be the back-bone for both Navy, and Marine air forces, it is being developed by Lockheed Martin and BAE systems to originally be a cheaper alternative to the F-22 "Raptor."
Costs, or how I learned how to love throwing money into a burning barrel
The F-35 has become perhaps the greatest example of the incredible amounts of waste and corruption in the Pentagon and the U.S. Military. It was planned to be the cheaper alternative to the F-22 "Raptor" but has ended up becoming the most expensive system ever developed in the U.S. bar none (and by extension, the world).
Contractors have shown enormous ingenuity in keeping the project alive against all reason. Direct lobbying is the merely the most simple method they use. Like the F-22, there is work done on the plane in almost every state in the U.S. This means many jobs all over the country are dependent on the continuation of the project. Nobody in Congress dares touch it for fear of being labeled a job-killer in their home state by political rivals.
Lobbyists even get involved in the technical side of the plane. Rolls Royce and Northrup Grumman lobbied the government to add a second engine to the plane. In itself, this is actually a good idea (see below); however, the final layout had already been finalized and was under development. Adding an extra engine at this stage is comparable to sticking a second engine under the backseat of a car. This modification requires a complete redesign of the F-35, wasting all work done beforehand. The fact that they were not laughed out of the Pentagon for this request should strike fear into any taxpayer.
Since the Pentagon is filled with Cold War warriors and technofreaks who want to possess every toy available, there is an incessant demand for the U.S. to possess the greatest, near-invincble planes to fight its wars. Reality shows that currently operational planes can get the job done just as well as they always have. In the post cold war world, America's traditional rival, Russia has demonstrated a non-interventionist approach for the most part and expresses little interest in developing next generation fighter jets.
Flaws, drawbacks, and other assorted
So, after umpteen billions thrown its way, it should be at least a good plane, right? Sadly (for anyone paying for it, or flying it for that matter), it's not. One MASSIVE oversight on it is that it only has one engine. This means that should anything happen to that engine, the plane is screwed. Even the smallest private personal jets have two engines. This problem is compounded almost exponentially as the F35 is a fighter aircraft, and as such is expected to be shot at. The smallest damage done to that engine and it becomes little more then a multi-billion dollar gravity tester.
The stealth of the F-35 is also very weak. Unlike the B-2 or F-117 that were built with stealth as the top priority, the F-35 has to do ten things at once, not doing anything particularly well. This also leaves the plane underarmed compared to others in its class.
Something the Canadians discovered was that the communications system is very spotty, and has a nasty habit of dropping when flying around in the high Arctic. Given that losing communications is grounds for scrapping a sortie and returning to base, this is a bit of a problem for a country looking for something to give them long term air superiority in the north.
Why it wouldn't matter if it had none of the above
The era of dogfights and air-to-air combat is in the past. In a world where international trade discourages large nations from going to war with each other, conflicts over the past 10 years tend to involve small scale, long term insurgences. Asymmetrical warfare is quickly becoming the standard form of conflict in the world. There is little place for advanced fighter jets, since no insurgencies or terrorist groups have an air force, and smaller, rogue nations tend not to have the advanced technology to make these airplanes more viable. Air power in asymmetrical warfare demands close ground attack craft, such as the A-10 "Warthog" or helicopter and fixed-wing gunships. Both of these aircraft types are being phased out, or have not received sufficient development since the Vietnam war.
Recent examples of air-to-air combat, as seen in the Libya intervention, demonstrate that "obsolete" fighters, sent by Canada and the UK, made very short work of any resistance that could be thrown at them.