Upvote:1
You have to mail your passport within 5 days of your appointment for the standard service or pay extra to fast track. Thereβs no guarantee you will receive the decision within the published timeframes, whichever option you choose, and in fact UKVI advises against paying the extra fee if you have an adverse immigration history.
https://www.gov.uk/government/publications/usa-apply-for-a-uk-visa/apply-for-a-uk-visa-in-the-usa