What happens if the U.S. misses its deadline to reunite families?

When federal judge Dana Sabraw gave orders to reunite separated families by certain dates, he made his demands clear: These were "firm deadlines," he warned. "Not aspirational goals."

That was weeks ago, before an earlier deadline in the case. Fast forward to Thursday, and US officials are scrambling to reunite hundreds of parents and children by the end of the day.

The big question is, what happens if the government fails to reunite all families who are eligible for reunification?

The short answer: No one really knows.

The American Civil Liberties Union -- which is suing the government on behalf of some families separated at the border -- hasn't requested a specific punishment if officials miss the deadline, which falls at 6 p.m. ET Thursday.

Judge Sabraw hasn't mentioned any specific consequences, either.

But we can look at what happened earlier for clues about what might happen.

July 10 was the deadline for the Trump administration to reunite all families with children under 5 years old who were eligible for reunification.

(Families might not be eligible if a parent has a serious criminal record, if a parent has a contagious disease or if the adult isn't verified as the child's parent.)

The Trump administration missed that July 10 deadline, failing to reunite all eligible families with children under 5 by the end of the day.

At the time, Sabraw said the ACLU would be able to suggest any consequences it deemed appropriate. But the ACLU didn't ask for any punishments, and the judge seemed mostly satisfied with the government's efforts to meet his July 10 deadline.

Two days later, the government said it had finished reuniting 58 eligible families with children under 5.

But that 58 figure paled in comparison to the estimated 2,500 families with older children, ages 5 to 17, who were separated and potentially eligible for reunification. And those families are at the crux of Thursday's deadline.

By Tuesday, the government said it had reunited 1,012 of those families. About 600 had been cleared for reunification but hadn't been reunited yet by Tuesday.

But as many as 914 parents won't be reunited with their children this week, the government said. In some cases, the parents can't be found or have serious criminal records. In other cases, they've already been deported without their children.

And a small number of parents haven't even been identified in the federal system, let alone tracked down.