Don’t even think about trying to sneak an oversized bag onto a Ryanair plane, the airline warns, because the airline staff is getting paid bonuses to turn you in.

“We will catch you,” warns the airline boss, Michael O’Leary, long known for looking for any possible way to squeeze more profits from passengers.

Mr. O’Leary is upping the bonus he pays employees to catch bag scofflaws and eliminating a cap on how much extra an employee can earn.

Far from apologizing for the aggressive pursuit of rule breakers, Mr. O’Leary is bragging about it in interviews with the British press. He says the policy will speed boarding and lower costs.

Mr. O’Leary tells the BBC that only a very small number of passengers try to sneak oversized bags onto planes and insists the airline is “not trying to catch people out.”

The airline has a reputation for being among the worst for customer service, travel writer Duncan Madden says. He notes that the airline has a “laser focus” on enforcing cabin baggage dimensions.

“It’s always a lottery whether you’ll get singled out at the gate to have your bag unceremoniously wedged into one of its bag size checkers,” Mr. Madden tells travel site Kayak.

“If there’s any question mark, expect to have your bag sent to the hold and pay an unreasonably large fee for the privilege.”

The airline has just increased the size limit for a carry-on bag to 40 x 30 x 20 centimeters to comply with new rules shared by European airlines. But if someone’s bag is as little as a centimeter too big, he or she will need to leave the bag at the aircraft door and pay about $60 for it to be transferred to the cargo hold.

The bonus payment per bag for airline employees who catch them is rising from the equivalent of about $1.50 to $2.50 and a monthly cap on earnings of $80 is being eliminated.

Ryanair has a long history under Mr. O’Leary of suggesting outlandish new ways to earn money while keeping fares low. 

In what some critics derided as publicity stunts, Mr. O’Leary once claimed that the airline was considering charging passengers to use the toilet; called for flights to have only one pilot instead of two, and claimed to have petitioned to conduct test flights with standing room sections where people would cling to subway-style handrails and straps during takeoffs and landings.

Mr. O’Leary acknowledged that the standing room idea was met with a “somewhat negative” response by regulators.

“We’re the airline with the lowest air fares in Europe,” Mr. O’Leary said. “Those are our rules. Please comply with the rules.”