The FDA has to give the factories 90 days notice of an upcoming inspection.
edit: The parent comment is flat-out incorrect. Not sure where you are getting your information from.
> FDA inspections are generally unannounced, with a few exceptions. From FDA's "What to expect during an FDA inspection" https://www.fda.gov/media/142762/download
https://www.fiercepharma.com/pharma/fda-must-solidify-plan-f...