The F-35 “Lightning” is in the news again. This is the joint development program to produce a new fighter aircraft, in three different variants, for the Air Force, the Navy and the Marine Corps. The Pentagon grounded the planes recently after an engine caught fire as one of the planes prepared for takeoff at Eglin Air Force Base in Florida. The pilot was able to safely exit the aircraft, but unexplained engine fires on a single-engine aircraft like the F-35 demand immediate attention, thus leading to the grounding.

Safety hazards with military aircraft are a serious matter, and the F-35 is certainly not the first aircraft to have troubles in the development process. But the F-35 is on track to be the most expensive weapons system in Pentagon history.

This recent incident is just another reason why Congress should consider a true “grounding” of the aircraft. The only way that can happen is if Congress starts to pull up on the purse strings and stops spending money on it. Unfortunately, recent reporting suggests that lawmakers are simply shrugging off this problem as typical of a major development program.

That may be. In fact, it probably is. And that’s why taxpayers should pay more attention to how the Pentagon develops weapon systems. The F-35 is just the latest poster child of a development program gone horribly astray. The problem is significant enough for the Government Accountability Office to have an annual report of at-risk Pentagon development programs. Number one on the list in 2013? The F-35.

Separate from its perennial presence in the “High Risk Report,” the GAO has also been tracking increases in the total program cost for the F-35. Back in October of 2001, GAO estimated total program costs for the plane at $233 billion. By March of 2012, GAO’s estimate had grown to $395.7 billion. Given the most recent estimate is more than two years old, my guess is the actual cost has crept even higher.

And as costs have gone up, the date for these aircraft to actually be able to fly and fight – what the Pentagon calls “initial operational capability” – has steadily moved to the right. The Marines will be the first to have operational F-35s – in fiscal year 2015, a full nine years after they expected to be flying them. For the Air Force, the date will be sometime in fiscal year 2016 – 11 years later than expected. The Navy will be the last to fly fully functioning F-35s: in fiscal year 2018. That will be 10 years after they first expected them in the fleet.

A recent analysis by my organization, Taxpayers for Common Sense, found that at least $39 billion has been spent on additional research and development that was never in the original cost estimates for the F-35. We were able to identify, from open sources, that the Air Force has spent $17.5 billion more on research and development of the F-35 in those intervening 11 years. For the Navy, the cost has increased about $4 billion. For the Marine Corps, the figure is $17.6 billion. To quote from our report, “In large part, that money went to contractors for additional research and several rounds of redevelopment when the contractors failed to meet the F-35 goals set by the Pentagon. There appears to have been no penalty to the contractors for those failures.”

And still the Congress looks the other way. This year’s request for the F-35, for procurement, more research and development, and a little bit of military construction is $4.7 billion for the Air Force and $3.3 billion for the Department of the Navy, which buys aircraft for both the naval service and the Marine Corps. That’s $8 billion just in the coming fiscal year. And still Congress thinks that isn’t enough. The House Appropriations Committee added four more F-35s to the Pentagon spending bill a few weeks ago. This would cost almost half a billion dollars more than the three services requested.

When the Senate Appropriations Committee takes up the Pentagon spending bill, currently scheduled for Tuesday, July 15, I hope they don’t go along with the House on this. It’s time to hold the contractors and the services accountable for the unconscionable waste of development dollars on the F-35. It’s time to end this program once and for all.