>>> GOOD EVENING AND IT'S GREAT TO HAVE YOU WITH US HERE ON A THURSDAY NIGHT. AND WE BEGIN TONIGHT WITH THE BREAKING HEADLINE LATE TODAY. THE PENTAGON BRIEFING REPORTERS JUST BEFORE WE CAME ON THE AIR, SAYING THEY ARE NOW TRACKING A SUSPECTED CHINESE SPY BALLOON HOVERING OVER THE NORTHERN U.S. IT WAS SPOTTED OVER MONTANA AND OTHER NORTHERN STATES. MONTANA, OF COURSE, HOME TO SEVERAL SENSITIVE NUCLEAR SITES. NOW, WE ARE TOLD THE SUSPECTED CHINESE SURVEILLANCE BALLOON IS THE SIZE OF THREE BUSES, WITH A TECHNOLOGY BASE SUSPENDED BELOW. AND FOR A TIME IN MONTANA, AIR TRAFFIC CONTROL IMPOSING A ██PG AIRPORT IN THE LAST 24 HOURS. AND LOOK AT THIS, THE CONTRAILS FROM F-22s SEEN IN THE SKY AS THEY CIRCLED AN AREA WHERE THE BALLOON WAS SPOTTED SOUTHWEST OF THE CITY. TONIGHT, A SENIOR DEFENSE OFFICIAL SAYS THAT PRESIDENT BIDEN WAS BRIEFED. THAT HE ASKED FOR MILITARY OPTIONS. SO, THIS EVENING, WHAT NEXT? AND IS THERE ANY POSSIBLE THREAT HERE? ABC'S TERRY MORAN LEADING US OFF FROM THE WHITE HOUSE TONIGHT. >> Reporter: TONIGHT, A SENIOR DEFENSE OFFICIAL SAYS AUTHORITIES ARE TRACKING A GIANT CHINESE SPY BALLOON THAT HAS BEEN HOVERING OVER THE NORTHERN U.S. FOR SEVERAL DAYS. >> THIS THING IS UP IN THE SKY, AND I HAVE NO IDEA WHAT IT IS. >> THE UNITED STATES GOVERNMENT HAS DETECTED AND IS TRACKING A HIGH-ALTITUDE SURVEILLANCE BALLOON THAT IS OVER THE CONTINENTAL UNITED STATES RIGHT NOW. >> Reporter: SOURCES TELL ABC NEWS THE UNMANNED HIGH-ALTITUDE BALLOON IS THE SIZE OF THREE BUSES WITH A TECHNOLOGY BAY UNDERNEATH. OFFICIALS SAY PRESIDENT BIDEN ASKED FOR MILITARY OPTIONS, BUT DECIDED TO FOLLOW THE RECOMMENDATION OF SENIOR MILITARY LEADERS NOT TO SHOOT THE BALLOON DOWN, DUE TO SAFETY RISKS FOR PEOPLE ON THE GROUND. THAT BALLOON SPOTTED OVER MONTANA, FORCING A TEMPORARY GROUND STOP WEDNESDAY AT THE AIRPORT INBILLINGS. THAT GROUND STOP COVERING A 50-MILE RADIUS. NO FLIGHTS, INCLUDING COMMERCIAL AIR TRAFFIC, WERE ALLOWED TO LAND OR TAKE OFF FOR AT LEAST AN HOUR. MONTANA IS HOME TO SEVERAL SENSITIVE NUCLEAR WEAPONS SITES. THE U.S. MOVED QUICKLY TO SHIELD THEM. >> ONCE THE BALLOON WAS DETECTED, THE U.S. GOVERNMENT ACTED IMMEDIATELY TO PROTECT AGAINST THE COLLECTION OF SENSITIVE INFORMATION. >> WELL, THIS IS REALLY SOMETHING. LET'S GET TO TERRY MORAN AT THE WHITE HOUSE TONIGHT. TERRY, WE KNOW THE PITTSBURGH TERRY, WE KNOW THE PENTAGON BRIEFING REPORTERS JUST BEFORE WE CAME ON TONIGHT, SO, WHAT ARE THEY SAYING ABOUT ANY POTENTIAL THREAT HERE? NO THREAT TO CIVILIANS? HAS THE U.S. REACHED OUT TO CHINA? >> Reporter: THAT'S RIGHT, DAVID, THE PENTAGON DOES SAY THAT THEY'VE BEEN TRACKING THIS BALLOON, THAT IT DOES NOT POSE A THREAT TO CIVILIANS. THEY ALSO SAY IT'S NOT THE FIRST TIME, THAT A HANDFUL OF OTHER TIMES OVER SEVERAL YEARS DATING BACK TO PAST ADMINISTRATIONS THEY'VE SEEN BALLOONS LIKE THIS. THEY SAY THEY DO NOT THINK IT POSES AN INTELLIGENCE RISK, AND THEY HAVE COMMUNICATED TO CHINA THAT THIS CANNOT CONTINUE. DAVID? >> STILL U