United Pilot Denied to Fly from San Francisco to Cancun: Here’s Why

SAN FRANCISCO- A United Airlines (UA) flight from San Francisco (SFO) to Cancún (CUN) was delayed over four hours after a passenger was caught smoking marijuana in the aircraft lavatory. The incident occurred aboard United Flight 1679, scheduled to depart on Tuesday (August 5, 2025), and led to the flight crew refusing to continue the journey.

The captain, concerned about secondhand exposure and potential FAA drug testing consequences, chose not to fly, triggering a crew replacement process and resulting in an extended delay for all passengers.

Photo: By Aero Icarus from Zürich, Switzerland – United Airlines Boeing 737-900ER; N37419@LAX;10.10.2011/622ha, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=26712819

United Pilot Denied to Fly

The situation escalated after a technical issue initially delayed Flight UA1679. As passengers waited onboard for paperwork clearance, one individual used marijuana in a front lavatory. The passenger was promptly removed, but the crew’s concern didn’t end there.

Citing the risk of secondhand exposure and the strict FAA drug testing rules, the pilot and crew ultimately chose to deplane.

In a statement reportedly made to passengers, the captain said, “I have 30 years left of my career at United, I’m not willing to risk getting drug tested when I get to Houston.” The airline then scrambled to assign a replacement crew, contributing to a total delay of over four hours.

United Airlines Boeing 737 MAX TAKEOFF from Chicago. Photo: Cado Photo

FAA Drug Testing Policy Creates Zero Margin for Risk

The Federal Aviation Administration enforces a zero-tolerance drug policy. Pilots are subject to random drug tests, and any trace of marijuana metabolites in urine — regardless of source or intention — can result in a failed test, triggering a suspension or revocation of certification. This holds true even if the exposure was secondhand.

That said, it’s important to note that the probability of testing positive from brief exposure to cannabis smoke in a well-ventilated airplane cabin is extremely low.

Studies show that passive exposure at DOT testing thresholds is virtually impossible unless someone is trapped in an unventilated, smoke-filled room for hours. Still, fear of job-ending consequences can make pilots err on the side of caution.

Flight crew are also required to self-report any perceived risk of impairment. Even the suspicion of compromised readiness can trigger an investigation. In this case, the captain acted in compliance with both regulations and personal caution, Viewfromthewing reported.

Photo: Clément Alloing

Smoking Marijuana on Aircraft Is an Offense

While recreational marijuana is legal in California, it remains illegal under federal law, which governs commercial aviation and all airports beyond TSA checkpoints. Possessing or consuming marijuana in these zones can lead to federal charges.

Even before passing security, airports operate under overlapping jurisdictions — but once inside the terminal or aboard an aircraft, federal law dominates. That’s why cannabis possession or use post-security, including in carry-ons or checked bags, remains a legal risk, regardless of state laws.

While TSA agents do not specifically search for drugs, if marijuana is discovered during screening, TSA can refer the incident to local or airport law enforcement. In this case, security was involved, and the offending passenger was removed from the aircraft.

The incident left passengers waiting for hours in San Francisco with minimal compensation. Each traveler reportedly received a $15 meal voucher — an amount that barely covers a snack at SFO.

Delays caused by security or crew incidents typically fall into a gray area for compensation, especially when airline policy compliance is involved.

Photo: JFK Spotting

Similar Incident

Crew refusals over unknown smoke exposure have happened before. In one case shared by a traveler, a pilot in Miami had to leave an aircraft after smoke triggered an alarm.

With no clear source and no alternate crew available, the flight was cancelled, stranding passengers for days.

These decisions, while frustrating for travelers, reflect the high stakes flight crews face under FAA regulations. Unlike passengers, pilots can’t afford uncertainty when their license and livelihood are on the line.

Stay tuned with us. Further, follow us on social media for the latest updates.

Join us on Telegram Group for the Latest Aviation Updates. Subsequently, follow us on Google News

The post United Pilot Denied to Fly from San Francisco to Cancun: Here’s Why appeared first on Aviation A2Z.