U.S. air-safety regulators want airlines to stay on top of potential safety issues like employee fatigue as carriers race to keep up with a surge in demand for flights.

Regulators haven’t seen any alarming trends emerge in data collected from airlines, Federal Aviation Administration officials said, but this week the agency alerted industry groups to potential problems that could lead to incidents or accidents. Carriers have been bringing back furloughed workers, taking planes out of storage and adjusting flights with consumers returning to air travel.

“While we are all excited about the burgeoning recovery of passenger traffic, airlines should look across their operations for additional ways to increase predictability and provide stability to the system. More certainty reduces safety risks,” FAA chief Steve Dickson said in a Thursday letter to industry groups.

In a memo that accompanied the letter, the FAA recommended that carriers remain vigilant about possible fatigue-related errors among front-line employees and distractions for pilots, such as discussions in the cockpit about the pandemic.

New York’s LaGuardia Airport. Air carriers are facing fresh challenges amid the spread of the Delta variant of the Covid-19 virus.

Photo: Spencer Platt/Getty Images

Other potential issues include birds nesting in long-dormant aircraft power generators, according to the memo. None of the potential risks flagged by the agency are believed to be widespread, FAA officials said.

The potential safety risks emerged through self-reporting by airlines and have been discussed by the Commercial Aviation Safety Team, a panel composed of industry and government officials. That group analyzes data to identify safety risks using information that carriers and employees can report without punishment when mistakes are identified, and voluntarily adopts safety improvements.

Carriers have been fully participating in that system, according to FAA officials, who credit it with a sharp reduction in U.S. aviation accidents over the last two decades.

Airlines For America, a trade group that represents large carriers, said it continues to work closely with the FAA and other agencies.

Passengers have rushed back to air travel this summer, encouraged by the distribution of Covid-19 vaccines and moves by elected officials to roll back restrictions on restaurants, entertainment venues and other destinations. The volume is a major reversal from last year, when many people who headed out on vacations avoided flights and companies cut business travel.

Airline and airport executives have said they believed demand for flights would pick back up, but the resurgence has been stronger than many anticipated.

Carriers are facing fresh challenges amid the spread of the Delta variant of the Covid-19 virus that could disrupt their operations. United Airlines Holdings Inc. on Friday said it would require its 67,000 U.S. employees to be vaccinated by the fall, a decision executives acknowledged some workers might object to.

Frontier Airlines said earlier this week it believed worries about the highly transmissible variant were weighing on demand, and some companies are delaying a return to office for workers, which airlines had been looking to generate business flights.

Amid the rebound, carriers have grappled with staffing challenges and difficult weather, as well as bringing back employees they furloughed and airplanes they mothballed when the pandemic decimated the industry last year. Customers have reported long phone waits for assistance and the volume of incidents involving unruly passengers has jumped, putting fresh stress on airline employees.

—Andrew Tangel contributed to this article.