If you are in danger or distress it is
...No.
No, that's actually disrespectful. Flying a flag upside down is a sign of distress. For instance, if you were on a sinking ship, you should turn your flag upside down to signal to other mariners that you are in distress.
When you are in distress and need help.
The American Flag flown upside down is a cry for help. It was mainly used on boats before the era of radio.
According to US law, flying the flag upside down is only allowed when trying to signal "dire distress in instances of extreme danger to life or property". Like, for example, if you're on a boat and it's on fire and sinking.Some people fly the flag upside down to protest the US government or its actions. This is technically illegal, but generally not enforced. Additionally, many Americans, especially military veterans, tend to view such an act with hostility.
Etiquette dictates that a national flag should never be shown upside down. It is a sign of distress to fly a flag upside down.
Flying an United States Flag upside down is a recognized distress signal.
None! Unless under duress.
You should never fly it upside down
At least not at sea. This is an international sign of duress.
Section 8a of the United States Code Title 4 Chapter 1 (otherwise known as the "Flag Code") reads: "The flag should never be displayed with the union down, except as a signal of dire distress in instances of extreme danger to life or property."
Three of the things one should never do out of respect to a national flag are: burn it deface it fly it upside down