"while"

@Sarah Zhou posted:

"Kullar says that while masking is mandate and typically enforced by flight attendants while aboard the plane, you should also be careful while at the airport, where it’s more crowded and mask-wearing may not be closely monitored by staff. " [from CNBC]

“while” is a conjunction that connect two sentences.

The first "while" acting as a conjunction means "although" and it is followed by a complete sentence, right?

I think that the second and third "while" also acts as a conjuntion and means "when". But why aren't they followed by a complete sentence？

Hi, Sarah—You are right that the first "while" is acting as what is traditionally called a subordinating conjunction and could be replaced by "although."

The phrase "masking is mandated and typically enforced by flight attendants while aboard the plane" would—if it stood alone—be a complete sentence.

You are also right about the second and third "while"s. Both "when" and "while" can introduce reduced clauses (e.g., "Be careful while [you are] at the airport").