MINISERIES PREMIERE: This three-part series is based on an interesting premise: that at any given time, enough human beings are aloft, traveling from one place to another in commercial and private aircraft, that the millions of them constitute a City in the Sky. (And no, for you fans of mythology or the Who, it’s not named Armenia.) This first installment is titled “Departure.” And its subject was recently made even more complex after a White House Muslim ban isn’t a ban, or is. The jury’s still out. And, as the case makes its way towards the Supreme Court, I mean that literally. Check local listings.