When Do You Need to Get to the Airport? We Did the Math

How early should you arrive for the busiest air-travel day in U.S. history? 

There have been seven such days since late May alone, fueled by strong leisure and business-travel demand. Friday is projected to break the record again, the Transportation Security Administration has warned. The agency expects to screen a record three million people at airport checkpoints. The previous record of just under three million was set on Sunday.Airports and airlines generally recommend two hours for domestic departures and three hours for international flights. But with so many people taking to the skies this summer, these standard guidelines for time to the airport might not apply.

To determine how much of a buffer you should give yourself, The Wall Street Journal asked travel experts which factors would add or reduce how much time that travelers need at the airport before a flight. Note: These recommendations are rough estimates—you’ll probably never need to arrive at 7 a.m. for a noon flight—and can’t account for factors like weather.

The baseline: 90 minutes

About 99% of travelers wait 30 minutes or less in the standard screening lanes at security checkpoints, TSA says. Boarding generally begins around 30 minutes before the scheduled domestic departures.

People traveling with only carry-on items need at bare minimum a 90-minute buffer before their flight, including the time it takes to walk to their gate.

Got your mobile boarding pass? Subtract 20 minutes

Preparation pays off. Try to check in for your flight before you leave for the airport. Getting your mobile boarding pass (or printing out a copy at home) lets you skip the wait for a check-in kiosk.

Traveling at a peak time? Add 30 minutes

Airports naturally see crunches in mornings and late afternoons. Likewise, weekends are busier than Wednesdays. And yes, the Starbucks in your terminal will have a line in the morning. Pro-tip: Place a mobile order before going through security.

Flying out of a major airport? Add 20 minutes

The top factor determining how much of a buffer travelers need is airport size, says Jen Campbell Boles, founder of Explore More Family Travel, a North Carolina-based travel agency.

More people and larger terminals often equal longer lines and walks. At New York’s John F. Kennedy International Airport, some gates are located at least a 15-minute walk from security. 

Parking or dropping off a rental car? Add 20 minutes

The process of returning a rental car is easier these days than it used to be, travel advisers say. The trouble here is getting from the rental agency to the terminal, potentially lugging bags on a bus or tram. Caroline Quinn, a travel specialist with the luxury travel agency Black Tomato, warns that at some airports, the car drop-off might be far off premises.

If you’re taking your own car to the airport, prepare for crowded parking lots. Reserve your parking spot in advance if you can—otherwise you might need to park in a more remote overflow lot.

Checking bags or flying with a pet? Add 30 to 45 minutes

Even when you can tag your own bags, travel advisers caution that checking a bag can take time. You can wait to print out luggage tags at a kiosk, then wait to weigh bags and drop them on the conveyor belt. Plus, most airlines require bags to be checked at least 30 to 45 minutes before departure. Check your airline’s website for its rules.

If you need to check anything oversize or unusual—such as golf clubs or skis—budget even more time, says Henley Vazquez, co-founder of the travel agency Fora. And if you plan to travel with Whiskers or Fido, err on the earlier side. Airlines generally must approve your pet to fly, which requires an agent’s help.

Flying internationally? Add 30 minutes

Going abroad is a more involved process. An agent will need to verify that you have a valid passport and other relevant travel documents. International flights often set earlier deadlines for checked luggage and begin boarding earlier.

Have TSA PreCheck or Clear? Subtract 20 minutes

A TSA spokesman says that 99% of people who have TSA PreCheck wait 10 minutes or less to go through security. And the screening itself is smoother, since you don’t need to empty your bag of electronics or remove shoes. (Some airports offer the ability to reserve a time for your traveling party’s security screening for free.)

These services might save less time than they used to because so many people now have access to them, travel advisers warn. And not all airports have Clear or dedicated PreCheck lanes.

Have executive status or a premium fare? Subtract 20 minutes

People with elevated frequent-flier status generally have access to dedicated check-in lines. At some airports, people who shelled out more for premium fares or those with elite status might have their own security lanes.

Traveling with young kids? Add 60 minutes

Escorting young kids through the airport and security checkpoints can require herculean efforts and inherently takes more time. Small children might need to go through separate metal detectors. Parents traveling with baby food, breast milk or formula in excess of liquid limits must have those items specially screened. 

Then there is the meltdown factor. A stressful travel day is the perfect recipe for a time-sucking temper tantrum.

Need a wheelchair? Add 90 minutes

Those who can’t handle lengthy walks across the terminal might need a wheelchair to navigate the airport. That takes a lot longer, says Lauren Doyle, president of the Travel Mechanic, a North Carolina-based agency. “You’re relying on someone else,” she says. On busy travel days, wheelchair attendants have their hands full, so allot plenty of extra time. (Also, if you need a wheelchair, make sure to reserve it in advance with the airline.)

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Write to Jacob Passy at jacob.passy@wsj.com