Americans have grown accustomed to the post-9/11 world of security checks. We understand that in the interest of public safety, we often have to put up with bag searches, pat-downs, metal detectors or all of the above to get where we're going — whether it's boarding a plane or entering a stadium.

But wait times to clear security at Minneapolis-St. Paul International Airport (MSP) last week were beyond the pale. The situation was so bad for travelers that Minnesota's two U.S. senators held a news conference to — once again — urge the federal Transportation Security Administration (TSA) to increase staffing at the airport.

Early last week, the Metropolitan Airports Commission (MAC) began construction on a multiyear, $1.6 billion renovation project that includes remodeling the ticketing lobby. Portions of the area are walled off for construction, creating less space in the middle of the terminal. So only security checkpoints at the north and south ends were open.

That prompted long lines, confusion and a lot of upset customers. And while last week was worse than usual, it was not an isolated incident.

As Sens. Amy Klobuchar and Tina Smith rightly pointed out in a letter to the TSA last week, MSP has been seriously understaffed for several years. It was the third letter Klobuchar had sent to the agency since last fall.

"The bottom line is that it is simply unacceptable that authorized TSA staffing at MSP has decreased while passenger traffic has increased," Klobuchar said at a joint news conference with Smith. "It is critical that we do everything possible to mitigate the impact on wait times caused by construction."

It's time the federal agency recognized that passenger numbers and characteristics have changed at MSP, and that those changes justify the need for more TSA agents. There is almost always some kind of reconfiguration or construction going on at MSP. The TSA and MAC can and must plan ahead to keep passenger traffic flowing. That doesn't mean simply adding staff here or there as a temporary fix.

As Klobuchar noted, in 2012 MSP served about 34 million passengers and had 670 full-time equivalent TSA officers at the airport. Five years later, 38 million passengers were served, but the TSA decreased the number of agents to 630.

In addition, a MAC spokesman told an editorial writer that the types of trips have changed and require more security workers. Five years ago, about 55% of passengers began or ended their trips in Minneapolis — now that that's up to 67%. That means fewer connecting customers who don't require security checks are coming through the terminals.

As a result of the inadequate staffing, long lines and confusion prevailed last week at both ends of the terminal — a situation that can create its own security problems. The north checkpoint could be used by all passengers, but the other end was reserved for those with TSA PreCheck, ($85 for five years) Clear with PreCheck ($179 annually) and airport employees. Those passengers pay extra to move more quickly through security, so it was especially unfair that they were held up in longer lines.

With busy travel times around the corner — October school conferences and November and December holidays — it's critical that TSA officials act soon to add staff and avoid the kind of meltdown MSP experienced last week.