Amid mounting chaos in US terminals, airport chiefs have recruited entertainers - including clowns - to lighten the mood.

Circus performers have been brought in to cheer up delayed passengers at San Diego International Airport, where travellers are missing flights because the Transportation Security Administration (TSA) is failing to get people through security quick enough.

WATCH: Airports are offering clowns, mini therapy horses, snacks and more to calm anger over long TSA lines. https://t.co/dDiIdc2oKy — Good Morning America (@GMA) May 17, 2016

It might seem like a joke, but the airport has enlisted Fern Street Circus to entertain delayed travellers, who have been expressing their frustrations on Twitter using the hashtag #iHateTheWait.

San Diego isn’t the only airport gripped by TSA chaos – queues are winding around terminals across the country as the busy summer season begins.

Neither is it the only airport to hire entertainment – Cincinnati/Northern Kentucky International Airport has been trying to stabilise the situation with miniature horses. Yes, horses.

Excited to have our therapy ponies back! Just in time for derby wkend 😉 #KentuckyDerby #KentuckyOaks @KentuckyDerby pic.twitter.com/FTh19eYhgb — CVG Airport (@CVGairport) May 6, 2016

As passengers face nightmare waits, airport chiefs have recruited the animals to rein in stress. The so-called “therapy unicorns” have been supplied by the Seven Oaks Miniature Therapy Horses programme in nearby Ohio.

“Animals help reduce stress and anxiety levels and put smiles on people's faces,” Mindy Kershner, an airport spokeswoman, told NBC news. “Unlike service animals, who are working and should not be touched, therapy animals can be patted and hugged.”

Other airports have laid on live music and free lollipops to lighten the mood.

It will take more than a lollipop to assuage American Airlines, though, which claims 6,800 of its passengers missed their flights in one week due to the delays.

“The lines at TSA checkpoints nationwide have become unacceptable,” lamented Ross Feinstein, a spokesperson for the airline.

The TSA blames its poor performance on an increase in airport traffic and budget cuts, but critics claim the tax-payer funded agency is inefficient and should be replaced by a private company.

Why hasnt the #TSA resolved obvious problems at airports?



It doesnt make sense that they would continue to function so dysfunctionally. — glen brown (@GlenBrown15) May 18, 2016

Passengers, meanwhile, are blaming the airlines for imposing fees on checked luggage, which has encouraged travellers to carry more hand baggage and exacerbated queues.

Airlines charge large fees for baggage -> more carry-ons -> backing up x-ray machines. What % of fees help pay for that? #iHateTheWait — scott slomiany (@doho123) May 17, 2016

The TSA has pledged to add 800 new security staff by June to ease queues, but passengers travelling to the US this summer should still be prepared for long waits. And short horses.