I am currently stuck in Spain, having contracted COVID-19 and missed my flight to the US. I've been in quarantine over a week, I feel fine, and I can legally go out in public according to both Spanish and US public health guidance. Howe, I keep testing positive on at-home rapid tests, so I can't reenter the US.

One possibility that has been suggested to me is to obtain a certificate of recovery instead of trying to get a negative test. This requires an official (ie, not at-home) positive test and a signed doctor's letter indicating recovery. The doctor's letter I should be able to get through either a telehealth visit with my PCP or an online service. However, I do not currently have an official positive test, because I've just been taking at home ones the whole time I've been in quarantine.

If I get a signed recovery letter and an official positive test on the same day, say tomorrow, can I use them together to fly the following day or two? The CDC airline guidance doesn't appear to prohibit this- it just lays out requirements for the type of test and says it needs to be administered in the last 90 days. However, I would've assumed the positive test would have needed to be at least 10 days old or something like that to prevent currently positive travelers from flying, so I want to double check. Will this work?

Edit and update: based on doc's answer and a conversation with my doctor, I agree that I shouldn't fly until I start testing negative.

However, the question still stands: I now have an 'official' positive test as of this morning, and my doctor has agreed to write me a recovery letter once I get a negative on at at home test. So, suppose I test negative at home tomorrow or Sunday, and get the letter from my doctor. Can I then use these documents to fly, or will it be a problem that the positive test is only a few days old?

Obviously the safest thing to do is to get another official test, but I'm currently in a small town in Spain where such tests are expensive and difficult to schedule, so flying with the recovery documents is preferable if it will work.

Update & bounty: I now have a 2 day old official positive test, a negative at-home test as of this morning, and a doctor's letter indicating that I am no longer contagious. The question remains whether I will be able to successfully board a flight in the next few days with just these two documents, or whether I need to get another official test (which is expensive and inconvenient, but doable if necessary).

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    What makes you think a doctor will give you a certificate of recovery if you tested positive in the last couple of days? In any case, this question is not trivial to answer, this use case would be up to the appreciation of the airline check-in agent or anyone checking the certificate really
    – meego
    Apr 28, 2022 at 8:06
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    @meego my understanding is that you are considered "recovered" after 10 days if your symptoms are resolved regardless of whether or not you continue to test positive, and that this is the reason for allowing a certificate of recovery instead of a negative test. I appreciate that this may not work in practice- hence the question - but I'm not trying to cheat the rules or anything.
    – Joe
    Apr 28, 2022 at 8:14
  • At least where I live there's two different types of technologies for rapid tests, along with PCR. Might be worth checking out if there's any other types of tests you can do and see if any come back neg
    – eps
    Apr 28, 2022 at 13:09
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    If you are still testing positive on a RAT test, you should NOT be hopping on a airplane. Do the right thing, and wait until your RAT test is negative. PCR tests can continue to test positive for some time after you are recovered, which is the reason for the "Certificate of recovery" concept - but with RAT tests it's generally accepted that if you are testing positive, then it's very likely you are still contagious.
    – Doc
    Apr 28, 2022 at 14:46

1 Answer 1


(The below is over-simplified and thus not necessarily technically correct on all levels - but it's good enough for a travel site!)

Broadly speaking there are two common types of tests used for COVID-19 (or more specifically, for the presence of the SARS-CoV-2 virus which causes it) - PCR and RAT.

PCR, which stands for Polymerase Chain Reaction looks for genetic material - DNA - of the SARS-CoV-2 virus. It can detect small quantities of this material in the sample, but does not differentiate between whether this genetic material is a live virus, or traces from a previous infection. As a result, it's possible for a PCR test to return a positive result for several weeks (or even in some case, several months) after the infection has passed.

In effect, this means that PCR tests are a great indicator of the fact you either are currently or have recently been infected with the SARS-CoV-2 virus, but they are NOT a good indicator of the fact you have recovered from an infection.

As this was a problem when using PCR testing, most countries allowed the concept of a "Certificate of Recovery", which allowed a doctor to confirm that you were (likely) no longer infected based on a number of factors, including a previous positive test, a time period since that test was taken, and the fact you were no longer showing symptoms. This could be used for the purposes of travel, even if you were still testing positive with a PCR test due to traces of the (dead) virus still being in your sample.

RAT, which stands for Rapid Antigen Test, doesn't look for genetic material, but instead they detect the presence of a specific viral antigen, which is an indication that you are currently infected with the SARS-CoV-2 virus.

Unlike a PCR test, RAT tests do NOT continue to return positive results once the virus is no longer in your system. If a RAT test is returning a positive result, then there is a very high probability that you are still infected, and likely still contagious.

There is no real need for the concept of a "Certificate of recovery" when using a RAT test, as once you have recovered the RAT results will show a negative result (unlikely PCR where they can remain positive). That's not to say that you can't obtain such a result from a doctor, and use it for travel, just that there's no specific need UNLESS you have a requirement to take a PCR test for the purposes of travel.

For your specific situation, where you are still testing positive with a RAT, the answer is simple - you should not travel! No respectable doctor will issue you with a Certificate of recovery if you are still testing positive with a RAT test (especially if your only proof of a positive test is only a day or two old!), and you are most likely still contagious so should not be travelling on public transportation.

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