Airports across the country are slowing down again—and some more than others. Find out which hubs are most likely to delay your flight.

(Mira / Alamy)

When technology consultant Steve McHargue travels to Panama on business, his biggest complaint is the airport where he frequently gets delayed.

“If I came home via a connecting flight thorough Anchorage,” says the Dallas area native, “and had to rent a husky team and race the Iditarod to get to my connecting flight, and when I got there they taped me up in a box and sent me to DFW via FedEx—that would all be better than having to go through Miami Airport.”

No doubt other travelers share his frustrations with Miami International Airport, which once again earned a spot among the 10 worst airports for delays. Every year, Travel + Leisure gathers data from the Bureau of Transportation Statistics to highlight which U.S. airports have experienced the least and most delayed departures over a 12-month period—in this case, flights that departed more than 15 minutes behind schedule from July 2010 to June 2011.

Chicago Midway ranked the No. 1 worst airport for delays, but overall, the bad news is that even the best airports slipped a little in performance compared to last year. Two previously top 10 airports—LAX and San Diego—have fallen out of favor, while two other airports dropped to the worst half for the first time. On the bright side, McHargue’s home airport, DFW, improved its performance enough to get out of the tardiest 10 for the first time since 2006.

While you can’t always control which airports you fly through, you can plan your travel in a way that lessens your odds of sitting at the gate. For each airport, we found the time of day when you have a 90 percent or better chance of leaving on time. We also found the time of day when performance falls below 75 percent—and sometimes way below.

If do you get stuck, some airports make better holding tanks than others. “A good one, and one that you’re likely to get stuck in, is San Francisco,” says Harriet Baskas, Seattle blogger and author of Stuck at the Airport. “It’s the only airport with an accredited museum,” she says. “They have great exhibits, and lots of good food options.”

Other airports, such as Washington’s Dulles, could use more diversions. “I always tell people with long layovers there to just get on a bus and go to the Air and Space Museum,” says Baskas.

Read on to see where San Francisco, Dulles, and other major airports ranked this year.

10 Worst

(Hartsfield-Jackson Atlanta International Airport)

No. 10 Hartsfield-Jackson Atlanta International Airport (ATL)Flights Delayed: 20.1%

Stuck in a rut: Atlanta has managed to improve its on-time departure performance a few points over the past years, but consistently finds itself dawdling its way into the worst 10.

Best Time Window: Before 9 a.m.

Worst Time Window: 4–10 p.m.

10 Worst

(Steve Hamblin / Alamy)

No. 9 Denver International Airport (DEN)Flights Delayed: 20.2%

What happened? Until now, the only bad-mouthing Denver’s remodeled airport has received is for its rather curious design. While most travelers aren’t bothered by architectural conspiracy theories, sitting around 20 percent of the time is another matter.

Best Time Window: Before 8 a.m.

Worst Time Window: 4–9 p.m.

10 Worst

(Courtesy of Miami-Dade Aviation Department)

No. 8 Miami International Airport (MIA)Flights Delayed: 21.2%

This Florida hub gets the Nice Try award: it’s still in the worst 10, but has improved its performance by four percentage points and climbed its way up from last year’s second-worst position. Your best bet here is to fly out by lunchtime.

Best Time Window: Before 8 a.m.

Worst Time Window: 3–9 p.m.

10 Worst

(Mira / Alamy)

No. 7 Chicago O’Hare International Airport (ORD)Flights Delayed: 21.4%

The best one can say about O’Hare’s standing is that it could have been worse, given its years-long bad reputation. (Back in 2008, your overall odds of getting delayed were 35 percent.) After a few years of steady improvement, on-time performance went down one percentage point this year.

Best Time Window: Before 7 a.m.

Worst Time Window: 5–11 p.m.

10 Worst

(The Port Authority of NY & NJ)

No. 7 Newark Liberty International Airport (EWR)Flights Delayed: 21.4%

Tying with O’Hare for on-time performance is kind of like winning an ugly dog contest. The consolation may be that while EWR offers basically the same chance of being late as it did last year, the airport still improved its rank by two slots.

Best Time Window: Before 8 a.m.

Worst Time Window: 3–11 p.m., and at its very worst 9–11 p.m.

10 Worst

(The Port Authority of NY & NJ)

No. 5 John F. Kennedy International Airport (JFK)Flights Delayed: 21.6%

New York’s busiest airport had been making up for lost time over the past four years, but has been lagging recently. On-time performance fell almost two points this year, dragging it down from No. 8. You can bide your time, though, in the wine or martini bars.

Best Time Window: Before 8 a.m.

Worst Time Window: 4–11 p.m.

10 Worst

(McCarran Int'l Airport)

No. 4 Las Vegas–McCarran International Airport (LAS)Flights Delayed: 21.8%

If you’re going to debut on the worst list, do it with fanfare. That’s what Las Vegas did, after having years of decent on-time performance. From some fliers, the bright side is more time to play those airport slot machines.

Best Time Window: Before 9 a.m.

Worst Time Window: 2–10 p.m.

10 Worst

(Alain McLaughlin/SFO Airport)

No. 3 San Francisco International Airport (SFO)Flights Delayed: 22.4%

Is it just that fog? Every year, SFO inches a little closer to the worst position—from eighth worst in 2008 to sixth worst last year. Things slow down early: on-time performance dips below 75 percent by 11 a.m., and doesn’t go back above that until evening.

Best Time Window: Before 8 a.m.

Worst Time Window: 11 a.m.–7 p.m.

10 Worst

(Baltimore/Washington International Airport )

No. 2 Baltimore/Washington International Airport (BWI)Flights Delayed: 23.2%

BWI debuted among the 10 worst airports for delays only last year, but it may be here to stay. Its on-time performance got worse by two percentage points this year and is the clear loser among the D.C.–area airports.

Best Time Window: Before 8 a.m.

Worst Time Window: 3–11 p.m.

10 Worst

(Douglas Coulter)

No. 1 Chicago Midway Airport (MDW)Flights Delayed: 29.9%

Midway worsened its performance by almost four percentage points this year. Your best chance here is to fly out bright and early: on-time performance dwindles late in the morning and languishes below 50 percent by 7 p.m.

Best Time Window: Before 8 a.m.

Worst Time Window: 11 a.m.–11 p.

The 10 Best Airports can be viewed at Travel + Leisure here.