Why was an Alaska Airlines Miami flight put on lockdown after passenger threats?

Two separate passenger incidents on US flights triggered emergency security procedures this week, including a temporary lockdown, calls to law enforcement and the removal of disruptive travelers.

The incidents involved United Airlines Flight 2801 in Milwaukee and Alaska Airlines Flight 305 in Miami, according to reports and air traffic control audio reviewed by CNN. The cases come as the Federal Aviation Administration continues to deal with hundreds of reports of unruly passenger behavior this year.

Federal authorities can seek civil penalties of more than $40,000 against passengers who threaten or interfere with airline crews, while serious cases can also result in criminal charges.

United flight diverted to Milwaukee

The first incident happened early Monday after United Airlines Flight 2801, travelling from Tampa to Chicago, was diverted to Milwaukee because of bad weather.

While the aircraft was on the ground in Milwaukee, a passenger allegedly made a threat that prompted the crew to contact authorities. CNN reviewed air traffic control audio from ATC.com, which captured the pilot informing controllers about the situation.

The pilot told controllers that a passenger had said they needed to leave the plane or would “commit some sort of crime,” according to the recording.

Sheriff's deputies were subsequently called to the aircraft and the plane was moved to the terminal. The final Milwaukee-to-Chicago leg was canceled.

United said passengers affected by the cancellation were offered reimbursement, hotel accommodation and rebooking on flights to Chicago.

Alaska Airlines flight returns to gate

A second incident unfolded Sunday evening at Miami International Airport involving Alaska Airlines Flight 305, which was scheduled to fly to Seattle-Tacoma International Airport.

Two passengers allegedly became disruptive while the aircraft was taxiing, prompting the pilots to turn the plane around and return to the gate.

Air traffic control audio obtained from ATC.com captured the pilot telling controllers that there was a customer disturbance and that threats had been made against flight attendants.

The crew then requested law enforcement assistance. The aircraft's engines were shut down and the flight was placed under a temporary lockdown protocol while authorities responded.

Miami-Dade Sheriff’s Office Airport District deputies met the aircraft at the gate, according to WBFS, which operates alongside WFOR/CBS Miami.

Authorities found no credible threat

An investigation later determined that there was no credible threat in the Miami incident, according to the sheriff's office, as reported by WFOR/CBS Miami.

Despite that finding, all passengers were required to leave the aircraft while authorities assessed the situation.

Alaska Airlines said the two disruptive passengers were removed and temporarily banned from flying with the carrier. Once the aircraft was cleared, the remaining passengers were allowed to reboard and the flight continued to Seattle.

The flight had been scheduled to depart at 6:29 p.m. Sunday but eventually left Miami at around 8:45 p.m., according to WFOR's reporting.

FAA warns passengers could face major fines

The incidents come amid continued scrutiny of disruptive behavior on commercial flights. The FAA said it can pursue enforcement action against passengers who assault, threaten, intimidate or interfere with airline crew members.

The agency said civil penalties can reach $43,658 per violation, while passengers involved in serious incidents may also face criminal prosecution.

With more than 830 unruly passenger reports received by the FAA this year, the latest cases show how quickly a confrontation or perceived threat can escalate into an airport security response, flight disruption and potential legal consequences.