The mysterious "slow-moving blob" detected in the skies over Washington Tuesday prompted a frantic response from security officials on the ground as they raced against the clock to assess the potential threat.

From the moment the object was picked up on radar, US officials across several agencies only had about 10 minutes to determine whether American lives were in danger and respond accordingly.

...

And while there are several different technical means for verifying whether a radar target poses a real threat or is an atmospheric anomaly or another natural occurrence, Leighton said Tuesday's incident highlights a potential problem for radar operators in the future.

"There's quite a bit of talk about some rogue states (like Iran) as well as terror groups using swarms of drones to conduct attacks. Such attacks could show up on radar as a "blob" and that would make it really difficult to get a positive ID on such a radar target," he said.

https://www.cnn.com/2019/11/28/politics/white-house-lockdown-scramble/index.html