This is a lot of aircraft orders by one country:

Leading the way is Dubai's own Emirates, which announced plans to spend $20 billion on 50 Airbus 380 superjumbos and another $76 billion on 150 of Boeing's smaller 777X widebodies. Boeing is selling another 109 of those 77Xes to the region's other two airlines, Qatar and Etihad which also placed ordered for 30 of its 787 Dreamliners from Boeing. Last but not least FlyDubai said it would buy 100 of Boeing 737 narrowbody jets.

From Matt Yglesias at Slate, that's a single country's two airlines buying 439 big jets. You won't be surprised, then, that writers at the Dubai air show are wondering about a bubble in Persian Gulf airlines. There's also concern about other bubbles in Dubai's economy.

Outside of the Gulf airlines' health, industry analysts worry about a bubble in narrow-body jets: "We believe that another bubble situation is currently developing, and will result in an oversupply of narrow-body aircraft."

Why should you care? Because a large chunk of Boeing's exports to foreign airlines are backed by the U.S. government (and thus you, the taxpayer) through a government agency called the Export-Import Bank of the United States.

If there is an aircraft bubble, you the taxpayer could foot some of the bill. Ex-Im takes steps to protect itself (and thus the taxpayers) from taking a bath if airlines are unable or unwilling to pay. But if the crash is bad enough, those steps may not be enough.