For those who must travel, or those who are itching to do so, airlines and airports are increasingly offering ways to get tested for the coronavirus ahead of a trip. Taking a test can assure you and others that you aren’t spreading the virus from one place to another.

In recent weeks, some destinations, like Hawaii, New York, Washington, D.C., and some Caribbean countries began allowing people who have tested negative for the virus and can show test results to skip mandatory 14-day quarantines, a process that some view as risky because it is possible that people can take a test, receive a negative result and then contract the virus later.

Are all coronavirus tests the same?

No. There are two categories of coronavirus tests: virus tests, which help determine if you have the coronavirus, and antibody tests, which detect if you have an immune response because of past exposure to the virus.

If you want to find out if you currently have Covid-19, you should plan on taking a virus test like a polymerase chain reaction or PCR test. PCR tests are currently considered the gold standard for tests because of their accuracy and reliability. PCR tests can detect an active infection and require a swab in the nose or the back of the throat. Some tests use saliva. The test is highly sensitive and looks for the virus’s genetic material.

Another type of diagnostic test is an antigen test, which detects the presence of a specific viral antigen or bits of coronavirus proteins, implying current viral infection. For antigen tests, a sample is collected by nasal swabbing, with hopes that there are some virus proteins in the sample.

You’ve probably heard of antibody tests, too, but those aren’t what you need in order to travel. An antibody test checks for antibodies, which may tell you if you had a past infection with the virus that causes Covid-19.

Are rapid tests reliable?

Many companies have released rapid tests and they are mostly antigen tests and they take minutes to return results. These tests tend to be less accurate, and false negatives could lead people to be reckless and unwittingly spread the virus, but they are fast and affordable. You can check if your airline and destination accept results from rapid antigen tests.

How do I know which test to take?

Most airlines and destinations will accept PCR tests although others might also be allowed.

If you’re taking a test specifically because you are about to travel, you should first see if your destination has a list of tests that it will accept. Many places, including Hawaii, Washington D.C., New York and a number of Caribbean countries, specify which tests they will accept.

If you get a test that isn’t approved, you could be forced to quarantine upon arrival or the airline could prevent you from boarding the flight.

Where do I get a test?

Many places are offering coronavirus tests, including some hospitals, urgent care clinics, pharmacies and doctor’s offices. Some churches and fire stations are offering testing, too. Airlines like Hawaiian Airlines, United Airlines, JetBlue and American Airlines are offering testing at the airport or at nearby drive-through sites for passengers heading to certain destinations. Some airports have clinics in terminals. Companies, including CareCube and Pixel by LabCorp, will mail a test to you and you send back a sample; they promise to send you your results within 12 to 34 hours and 36 hours, respectively. JetBlue has a partnership with Vault Health for mail-in tests.

It’s a good idea to start by reaching out to your doctor’s office to see what all the available options for testing are and how long it will take to get results. If you don’t have a primary care provider, a good place to start is on city and state health department websites, which outline the various testing options and locations.

I have a trip coming up. When should I take my test?

You should get a coronavirus test before you travel. Figuring out the exact time can be tricky, but you can’t wait too long to take the test because you might not get the results back in time to go on your trip.

For those reasons, many destinations, including France, Aruba, Bonaire, Puerto Rico and Hawaii, require that the test be taken within 72 hours of departure. Abu Dhabi and Croatia require test results are within 48 hours of departure. Some airlines, like Egypt Air, allow travelers to use results from a test taken up to 96 hours before traveling, depending on where they are traveling from and to.