Imagine this sequence of events:
1. A perfectly legal subpoena is issued for someone to appear as a witness, while they're a plane's flight away from home.
2. Put witness on no-fly list.
3. Cite witness for contempt of court for failing to appear.
For example: Federal Rule of Civil Procedure 45(b) requires that you serve the person with the subpoena. If you wait until they're away from home, you're going to have a much harder time finding them. Not a complete barrier to the scheme, but ask your lawyer friends how much fun it is to track down someone who cannot be found at their nominal residence or place of business. They will have stories. They will not be fun stories.
Also, Federal Rule of Civil Procedure 45(d)(1) provides that:
A party or attorney responsible for issuing and serving a subpoena must take reasonable steps to avoid imposing undue burden or expense on a person subject to the subpoena. The court for the district where compliance is required must enforce this duty and impose an appropriate sanctionâ"which may include lost earnings and reasonable attorney's feesâ"on a party or attorney who fails to comply.
That rule doesn't appear to apply here because I understand that this was a party witness, not an opposition or hostile witness who you'd compel to attend using a subpoena. Instead, Judge Alsop is likely to cite "the inherent authority of the Court" (to conduct proceedings and sanction parties who unreasonably interfere with those proceedings). But if you're the government, or a party that fraudulently causes the government to put someone on the no-fly list, that Rule would apply to shennanigans involving any witness that you were compelling to attend.
Boom, you now have a tool for the intelligence community, with the help of a friendly (or blackmailed) judge to put anyone away they like, for any reason they like, at least for a little while.
No. Because contempt of court typically requires an intentional act, and typically is used as a threat by that judge to gain compliance. If you were to show up ready to testify, you very likely would not be jailed for contempt merely due to the fact that you've voluntarily showed up. If you can also show that you were actively impeded from showing up, you almost certainly would not be jailed for contempt.
At worst, you could be arrested where you were stuck, temporarily jailed, and extradited to the state/court that issued the subpoena. Slightly traumatic, but remarkably quick if you don't oppose the proceedings. Better yet, the authorities attempting to extradite you will rather quickly find out that you are on the no-fly list. Unless they're part of the 'grand conspiracy' too, that tends to work against the scheme.
Of course once you start theorizing as to "friendly (or blackmailed) judge[s]," you can come up with all sorts of whacky crap. Like a Federal judge ignoring the typical requirement that a subpoena cannot demand attendance in less some number of days (related to Rule 45(d) -- try to issue a subpoena requiring attendance the next day and see how enforcable that will be) and the laws of physics somehow preventing you from getting a train ticket, bus ticket, or rental car allowing you to return home within the typical required 'waiting period.'
Too much Hollywood. Not enough real life. Courts tend to work slowly and methodically. Judges tend not to throw away their careers on petty crap, and with the exception of a very few (Supreme Court types) remain answerable to a host of other judges. Actual long-term jailing for contempt is relatively rare and exceptional. You would do well to focus your conern on your local LEOs and prosecutors, who really can screw up your life with very little cause.