Unconfirmed reports say Lakenheath, plus nearby RAF Mildenhall and RAF Feltwell, jumped to Force Protection Condition Delta. That's the highest alert level the US military has.
A US Air Force spokesperson says no troops, aircraft or buildings were affected. The UK Ministry of Defence says it's resolved now. Nick Timothy, the Conservative MP for West Suffolk, says he was told there's no threat to the public.
That's everything we know.
Why this mattersSo why does this base matter so much?
RAF Lakenheath is one of the most important US Air Force bases in Europe. It's home to the 48th Fighter Wing, the Liberty Wing. They fly F-15E Strike Eagle jets and F-35A Lightning IIs. Almost 7,000 active-duty troops are based there.
And this base has been on edge for weeks.
Earlier this week, Lakenheath and Mildenhall both raised their alert to FPCON Charlie, the second-highest level. No clear public reason was given at the time. Lakenheath had already hit that same alert level once before, back in September.
Then, earlier this week, at least 12 US Air Force aircraft left Mildenhall, including two refuelling planes. One report, from the Wall Street Journal, said it was a response to an Iran threat. The BBC says it hasn't confirmed that independently.
Tonight isn't the only security scare this year either. In September, a group of men in white vans, some carrying fuel, were spotted near RAF Fairford in Gloucestershire. That triggered a major incident declaration. The B-1 bombers stationed there were flown back to the US the next month.
Andy Burnham, the UK Prime Minister, said Iran played a part in that incident. Iran denied any responsibility.
Two British men were charged last month over the Fairford case. One is accused of assisting a foreign intelligence service believed to be Iran's. The other is accused of entering a prohibited place for what prosecutors called a prejudicial purpose.
Then this week, separately, the US Justice Department charged three men it called Iranian operatives over the same alleged plot. One of them, named as Mohammad Ali al-Hassani, is accused of directing people to the base and funding the purchase of metal objects that could be used as shrapnel.
And this week, Mohsen Rezaei, identified as Iran's security chief, said in a broadcast interview that Iran would hit US bases beyond the Middle East, including in Europe, if they were used to attack Iran.
Downing Street says British airbases are safe and that keeping them secure is a top priority.
So here's what we don't know. Who sent the drone. Where it came from. How close it got. And whether tonight connects to the Fairford case at all.
Neither the US Air Force nor the Ministry of Defence has said whether they think Iran is behind it.
