Already faced with lines that snake through terminals out to the curb, fliers are bracing for long waits at security in the busy summer months. Some major airports are currently seeing wait times exceeding 90 minutes at peak hours.

Here's a look at the problem and what travelers should expect.

Q: Why are the waits so long?

A: More people are flying, thanks to a mix of a strong economy, more flights and lower fares. At the same time, the Transportation Security Administration and Congress cut the number screeners by 10 percent on expectations that an expedited screening program called PreCheck would speed up the lines. However, not enough people enrolled. The TSA had been randomly placing passengers into the faster PreCheck lanes but that stopped in the fall after government auditors found lapses in security.

Q: Will there be long lines for my flight?

A: There is no easy way to tell. The worst waits have been at the largest airports, which see the majority of fliers, and only during peak hours. But during slower hours, the TSA staffs fewer lanes and that might cause backups. Even those enrolled in PreCheck have no way of knowing if those express lanes will be open when they arrive at the airport. The TSA suggests passengers arrive at least two hours before domestic flights but some in the airline industry are now saying that might not be enough. However, at certain times of the day, lines are nonexistent.

Q: What is the government doing about it?

A: Congress agreed to shift forward $34 million in TSA funding, allowing the agency to pay overtime to its existing staff and hire an extra 768 screeners by June 15. But there is no grand plan to return staffing to former levels. Some passengers can still randomly be placed in PreCheck based on their age or if an explosive-detecting dogs first screen them, but those are small numbers. The TSA is relocating screeners and canine teams to the 20 busiest airports, such as Chicago's O'Hare.

Q: What can I do to speed up the line?

A: Each passenger should have their ID and boarding pass ready. Before reaching the X-ray machine, empty your pockets and place your keys, cellphone, change and any metallic jewelry into your carry-on bag. Wearing slip-on, slip-off shoes also helps.

Q: What if I miss my flight?

A: Passengers have been missing flights. For now, airlines have been finding space for them on later flights. But during the busiest summer travel days there are very few empty seats to accommodate anybody who misses a flight.

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Follow Scott Mayerowitz at twitter.com/GlobeTrotScott . His work can be found at http://bigstory.ap.org/content/scott-mayerowitz