Breast implants do not expand or contract any more than you do while taking off or landing.
There was a you lady of Nizes
Who had breasts of two different sizes.
One was so small it was nothing at all
But the other was large and won prizes!
... unless there happens to be some sort of bubbles or dissolved gas in them. I think this has to be the first thing you think of, if you accept the premise that the plane flight caused the implants to rupture.
I was thinking the same thing. This is highly unlikely unless there was a massive defect in the implant. There are many women flying every day with implants without problems.
BTW - Myth Busters did a show on implants and they are very tough. And they get paid too.... what a job.....