For someone with an elevated position in Al Qaeda, Mr. Shami has kept an unusually low profile. He has made no propaganda videos, nor does he seem to have been mentioned in any of the myriad online forums that militant groups use to motivate their followers, raise money and recruit new fighters.

The SITE Intelligence Group, which monitors the online communications and propaganda videos of militant groups, said it had no records of Mr. Shami’s name ever being discussed in chat rooms.

Some terrorism experts said that it could be a calculated strategy by Al Qaeda not to broadcast the growing role of an American inside the organization, or that the group might refer to Mr. Shami by another name. Still others said that it might just be an act of self-preservation on Mr. Shami’s part, given that so many of the people who have planned external operations for Al Qaeda — including Ilyas Kashmiri and Saleh al-Somali — were killed by American drones.

“At some point, it would probably make sense not to advertise these positions,” said Seth Jones, a terrorism expert at the RAND Corporation. Mr. Jones said that Mr. Shami had made “a very conscious effort to stay below the radar.”