The Centers for Disease Control and Prevention is investigating two American Airlines flights after passengers on board complained of flu-like symptoms.

Twelve passengers on two different American Airlines flights between Europe and Philadelphia reported flu-like symptoms when they arrived in the U.S. Philadelphia’s airport held all 250 passengers from both flights (American Flight 755 from Paris and Flight 717 from Munich) for medical review as a precaution, USA Today reports.

The twelve sick passengers had sore throats and coughs but did not have fevers. Those passengers were released and will be notified of their test results in the next 24 hours.

All of the other passengers on both flights were allowed to continue with their travel.

The health incidents happened yesterday after the passengers left the planes and were headed to customs, so neither of the planes involved were quarantined. The incidents occurred just one day after passengers on an Emirates flight from Dubai to New York tested positive for the flu and other respiratory viruses.

Today, American Airlines had a different kind of problem when a passenger on a flight from Phoenix to Kona, Hawaii flushed a diaper in one of the lavatories, causing all of the plane’s lavatories to be taken out of commission. Passengers aboard that flight were asked to urinate in plastic bottles or bags, or to wait until getting to the airport. All of the passengers on board that flight were given 30,000 airline miles, enough for a free round-trip ticket.