The 113, including children and pregnant women, landed in Nuevo Laredo on Tuesday.
They were among thousands stranded in Costa Rica after neighbouring Nicaragua denied them passage north.
Cubans are allowed automatic residence when they set foot in the US.
But after the two counties normalised ties following years of animosity, the number of Cubans trying to reach the US surged amid fears the policy would be dropped.
Central American nations reached a deal last month allowing migrants stranded in Costa Rica to continue on to the US.
The first flight carrying about 180 flew from Costa Rica to El Salvador in January.

Champagne tastes like sheet metal after the third glass. Sunbathing gives you cancer. And the ubiquity of Henry Moore sculptures in English market towns in the 1970s put me off his work for a quarter of a century.
Back then, in Harold Wilson's Britain, Moore's monumental stone figures and giant abstract casts had the same worthy municipal feel as the local town hall.
Any conurbation large enough to support a Boots, a cinema and a public convenience seemed compelled to plonk an enormous Moore sculpture on a prize piece of public real estate.
His misshapen family groups and huge pierced boulders of bronze were like those fashionable avocado bathrooms - not nearly as groovy as the older generation thought. More Abigail's Party than the Sex Pistols.
I wasn't alone in wanting no more Moore.
In 1967, he offered the Tate Gallery "20 or 30 major pieces". Fellow artists were less keen, saying it was wrong to devote so much space to a single living artist (Moore had insisted his gift be on permanent display, which would have taken up a sizable chunk of the Tate's sculpture galleries).
The Tate declined - and the artist gave the work to a grateful Art Gallery of Ontario instead.
That was then.
Forty years later, I have aged, and so have Moore's sculptures. They have fared much better than me - they look terrific now.
Maybe it's their sense of calm permanence in our superficial, super-fast world, or my romanticising of Moore's post-war vision of modernity.
Either way, it was a pleasure to spend yesterday at his old home in Perry Green, Hertfordshire, which is now The Henry Moore Foundation.
He was a sincere and dedicated artist who knew he wanted to be a sculptor aged 11, had his first commissions in his teens, and went on to excel at the Leeds School of Art.
There he met and befriended another aspiring young sculptor called Barbara Hepworth, who, like Moore, was inspired by the Yorkshire landscape of their birth.
He read widely, immersed himself in art and drew on influences far and wide, from primitive African artefacts to Parisian Cubism.
His intellectual and technical wherewithal enabled him to successfully incorporate all these ingredients into harmonious, pleasing forms that feel both ancient and modern.
It's what gives his work such broad appeal and why it can be seen in hundreds of cities around the world - there is something in it for everyone.
His drawings of sheep and apple trees have an intensity and energy that feels kinetic. You'll see plenty of the real thing if you sit at his old oak desk in the little shed with a picture window that looks out onto the fields of sheep that frequently wander over to look at you.
There are some good drawings from his student days, which you can see in an exhibition opening this Saturday at the Foundation called Becoming Henry Moore.
There are plenty of sculptures, too, in the exhibition and dotted about the 70 acres of landscape, which the canny Moore used as a showroom for potential clients.
They look good. Much better than they did in those tired old market towns.
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A group of vulnerable Cuban migrants have been flown by the Costa Rican authorities to a Mexican border town, from where they are expected to enter the US.
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You really can have too much of a good thing.