The North American Aerospace Defense Command, or NORAD, said it detected Russian military aircraft off the coast of Alaska on Sunday, marking the fourth time since 9/11 amid heightened tensions between the U.S. and Russia.

Two Russian IL-38 military planes operating in the Alaska Air Defense Identification Zone, or ADIZ, were detected and tracked on Sunday, NORAD said in a news release.

The aircraft remained in international airspace and did not enter U.S. or Canadian sovereign airspace, NORAD said, adding that this Russian activity in the Alaska ADIZ happens regularly and is not believed to be a threat.

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The aircraft in the other three incidents in the past week — on Wednesday, Friday and Saturday — also remained in international airspace in Alaska's ADIZ and were not viewed as a threat, according to NORAD.

The U.S. and Canada, which together make up NORAD, first intercepted a couple of Russian military aircraft on Wednesday.

A pair of TU-142s were detected by NORAD on Friday. And on Saturday, two Russian IL-38 planes were intercepted, the same type of aircraft intercepted in Sunday's incident.

An ADIZ begins where sovereign airspace ends and is a defined stretch of international airspace requiring the ready identification of all aircraft in the interest of national security, NORAD said.

NORAD said it employs a layered defense network of satellites, ground-based and airborne radars and fighter aircraft to detect and track aircraft and inform appropriate actions. The company said it is prepared to employ a number of response options to defend North America.

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Earlier this summer, NORAD intercepted two Russian and two Chinese bombers flying near Alaska for the first time that the two countries have been intercepted while operating together, U.S. officials said at the time.

Vice President Kamala Harris has gone 57 days as the presumptive, and now, official Democratic nominee for president without holding an official press conference. 

Under pressure to sit down for a substantive interview after weeks of stonewalling, Harris finally ended her interview drought last month in Georgia when she was joined by running mate Tim Walz for a pre-taped piece with CNN's Dana Bash that was a far cry from a traditional press conference.

Trump held his third news conference since the beginning of August on Friday in California, taking the opportunity to roast his opponent's home state and hold forth on a number of topics, including crime, immigration and inflation.

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Harris sat for two taped radio interviews last week, and she gave her first solo television interview as the Democratic nominee on Friday in Philadelphia.

As for when she'll actually do a formal press conference, that day may never come, at least while she's still a candidate.

Conservative Radio Libre host Jorge Bonilla feels Harris should do a press conference but said it’s almost "irrelevant" because she continues to get a pass. 

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"She is highly unlikely to do a press conference because the media have enabled and encouraged her ‘plexiglass basement’ strategy, wherein she preserves the illusion of being out there while remaining wholly inaccessible to the press and therefore unaccountable," Bonilla told Fox News Digital.

Trump has sought to highlight the contrast in media availability between the two, sitting for several lengthy interviews in recent weeks, in addition to his three news conferences.

In her interview on Friday in Philadelphia, her answer citing her middle-class upbringing when asked about specifics of her economic policy drew sharp criticism.

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"You know, I grew up in a neighborhood of folks who were very proud of their lawn," she said. "And I was raised to believe and to know that all people deserve dignity, and that we as Americans have a beautiful character. You know, we have ambitions and aspirations and dreams, but not everyone necessarily has access to the resources that can help them fuel those dreams and ambitions. 

"So when I talk about building an opportunity economy, it is very much with the mind of investing in the ambitions and aspirations and the incredible work ethic of the American people and creating opportunity for people, for example, to start a small business."

Fox News Digital’s Paul Steinhauser contributed to this report.