The Aviation Department said flight tracking applications showed the nearest civilian aircraft was about 45 nautical miles from the drone dropped by an Iranian missile, Reuters said.
"There were a lot of civilian aircraft operating in the area at the time of the objection process," it said.
It remained concerned at the escalation of tension and military activity in close proximity to civilian aircraft routes and Iran's readiness to use long-range missiles in international airspace without warning in sufficient time.
The Iranian Revolutionary Guards announced the downing of a US spy plane on Thursday morning in the southern province of Hormuzgan.
The Pentagon said on Wednesday that the latest deployment of 1,000 US troops in the Middle East, announced on Monday includes a battalion of Patriot missiles and marines and reconnaissance aircraft and "other deterrent troops."