The government has released another report about airline on-time performance, and it’s both horrifying and monotonous.

According to the latest U.S. Department of Transportation survey, just 71.1 percent of the nation’s flights arrived on time in August. That’s down almost 5 percentage points from August 2006, continuing the yearlong decline in airline efficiency. Cumulative, year-to-date on-time airline performance is the worst it has been in 13 years. Then there’s this: 159 flights in August spent more than three hours on the nation’s runways waiting to takeoff. Three flights sat on the tarmac for more than five hours.

I have no silver lining to offer here. Things are bad and getting worse.

But while there’s no good news, at least there is a copious amount of data to help you protect yourself and minimize your delays. You can spend ages poring over the 44-page D.O.T. report, or you can just use my cheat sheet. I’ve dissected the D.O.T.’s numbers and added some thoughts about the best and worst times to fly into the nation’s busiest airports.

Atlanta
On average, almost one in three flights arrive late to Hartsfield airport, where both Delta Air Lines and AirTran Airways operate hubs. Your best shot for an on-time arrival is before 2 p.m., when flights run on schedule 77 to 86 percent of the time. Abandon all hope in the evening; between 7 and 10 p.m., the airport’s on-time rate is in the low 40s.

Boston
On average, 70 percent of flights into Logan International Airport are on time for the day. Your best window for timely arrivals is 7 to 10 a.m., when 80 percent of flights are on time. From 6 p.m. on, however, you have almost a 50-50 chance of getting in late.

Charlotte, North Carolina
US Airways dominates Charlotte-Douglas International, where the average daily on-time rate is about 73 percent. Arrive before 3 p.m. and you’re in great shape. After 4 p.m., however, Charlotte deteriorates; 6 p.m. to 8 p.m. is worst, with on-time arrivals at about 60 percent.

Chicago
O’Hare International, a hub for the nation’s two largest airlines, American and United, is a lousy place to fly. On average, one in three flights run late throughout the day. If you can get in before 10 a.m., you’re least likely to be delayed. But after 7 p.m., every other flight arrives late. The situation is slightly better at Midway, where 80 to 90 percent of flights are timely before 4 p.m. But four in 10 flights reaching Midway after 6 p.m. are late.

Dallas-Fort Worth
Dallas-Fort Worth, the home of American Airlines, looked good in August, with about 75 percent of arrivals on time. It was much worse earlier in the summer. Right now, you’ll be fine before 2 p.m. But avoid arrivals after 8 p.m., when less than 50 percent of flights are on time.

Denver
Denver’s freaky winter weather creates havoc at Denver International, but flights are currently running 74 percent on-time. The airport is great for arrivals before 2 p.m. But with two airlines—United and Frontier—having their hubs here, evening arrivals are a crapshoot. After 5 p.m., about four in 10 come in late.

Detroit
Northwest Airlines controls Detroit Metro, where 72 percent of flights arrive on time throughout the day. Your best travel time is the 2 p.m. to 5 p.m. window. Try to avoid flights scheduled to arrive after 9 p.m., when performance slumps into the 50s.

Fort Lauderdale, Florida
Fort Lauderdale has the nation’s most schizophrenic airport. Arrive before noon and you’ve got a nine in 10 shot of being on time. Arrive after 8 p.m., however, and you’ve got a 50-50 shot of being late.

Houston
George Bush Intercontinental Airport, where Continental has a big hub, is one of the nation’s best airports for connecting flights. Over the course of the day, 82 percent of flights are on time. And other than between 8 p.m. and 11 p.m., when one in three flights run late, the airport is reliable.

Los Angeles
As major-city airports go, LAX is decent, with an on-time average of about 75 percent during the day. But avoid end-of-day arrivals; almost 40 percent of flights are late after 8 p.m.

Miami
American Airlines dominates Miami International, and many Latin American carriers fly here too. About 70 percent of the flights are on time during the day. And like most Florida airports, Miami is very, very good in the morning (more than 85 percent of flights on time before 11 a.m.) and very, very bad in the evening (about 50 percent of flights on time after 9 p.m.).

New York
It’s hard to overstate how bad things are at New York’s three major airports. Some experts say that a third of all the delays in the nation happen here. On average, just 57.6 percent of flights arrive on time at LaGuardia International. John F. Kennedy International (58.7 percent) and Newark Liberty (61.9 percent) are only slightly better. At LGA, there is no good time to arrive, although you’ll do least poorly if you can get in before 10 a.m. At JFK, you’ll do okay until noon (about 75 percent on time), before the transatlantic arrivals flood the airport. At Newark, you’re in decent shape until 1 p.m., but on-time performance begins plummeting toward 40 percent after 3 p.m.

Philadelphia
US Airways controls Philadelphia International, and it’s a mess—worse than New York’s airports, in fact, when you factor in US Airways’ alarming propensity for losing luggage. Just 61 percent of flights are on time, and unless you arrive before noon, you’re toast.

Phoenix
At Phoenix Sky Harbor International, which is blessed with good weather year-round, about 75 percent of flights are on time during the day. Try for an early flight; 85 percent of arrivals before noon are on time. After 6 p.m., though, one in three flights is tardy.

Salt Lake City
Salt Lake City International may be the best place in the country to change planes—Delta Air Lines has a hub here—because its on-time performance average is 80 percent. Just beware of arrivals after 8 p.m., since delays elsewhere around the Delta system mean Salt Lake City runs late too.

San Francisco
The fog that shrouds San Francisco International makes it a tricky place to keep to schedules, and an average of one in three planes run late during the day. But too much traffic arriving in the evening means the airport runs just 50-50 after 9 p.m. Things are better across the bay at Oakland International, where 77 percent of the planes arrive on time. Once again, however, the nighttime is not the right time, because arrivals after 8 p.m. run late about 40 percent of the time.

Seattle
Seattle is home to Alaska Airlines and to notoriously airline-unfriendly weather. Sea-Tac operates at about 68 percent on-time during the day. You’re okay if you can arrive before 10 a.m., but you’ll run late four times out of 10 after 7 p.m.

Washington
The three airports serving Washington—Baltimore-Washington International, Dulles International, and Reagan National—are all mediocre performers. Mornings are okay—about 80 to 85 percent of arrivals are on time—but evenings are a nightmare. On-time performance deteriorates rapidly after 4 p.m. Must to avoid: the last flights into Reagan National; on-time performance after 8 p.m. drops below 60 percent.

The Fine Print
If there’s a moral in the numbers, it’s this: Fly early in the day. Airlines run their aircraft into and out of connecting hubs, so when a flight arrives late, it affects that aircraft’s next scheduled departure. Delays subsequently cascade throughout the day. By the evening hours, aircraft are so far off schedule that flights have no chance of running punctually.