UPDATE, 8:57 AM: ABC, CBS, Fox and NBC as well as the cable networks have just broken away from normal programming to cover President Obama‘s remarks live from the White House on the latest from yesterday’s Malaysia Airlines disaster over the Ukraine. Obama said one U.S. citizen was among the 298 passengers killed from what is suspected to be a surface-to-air missile launched by pro-Russian rebels. He called for an immediate ceasefire in Ukraine and demanded a credible investigation, saying a UN investigation is already underway with Ukraine and Russia expected to cooperate fully.

cnn ma shot down july 17PREVIOUS, THURSDAY AM: Even before the Israeli ground invasion of Gaza began today, the cable news networks and broadcasters had decided to expand coverage because of the tragic Malaysia Airlines disaster in the Ukraine. Both CNN and Fox News Channel will be turning their primetime blocks into live coverage of the crash as well as the situation in the Middle East. Also FNC’s The Kelly File host Megyn Kelly will be anchoring an additional hour live from 11 PM-midnight tonight. With more coverage for tomorrow morning, Fox & Friends is now going to come on at 4 AM ET as opposed to its usual 6 AM. All of MSNBC‘s primetime programs are dedicated to the Malaysia Airlines incident. CNBC will be broadcasting a Special Report nchored by Tyler Mathisen and Michelle Caruso-Cabrera on both situations at 7 PM ET.

Additionally, ABC, CBS and NBC are all expanding their nightly news broadcast to 1 hour tonight beginning at 6:30 PM ET. While NBC and CBS will see their regular anchors Brian Williams and Scott Pelley in the big chair, ABC will see soon-to-be-full-time anchor David Muir handling the duty for World News tonight. This isn’t a sudden acceleration of Muir’s June 25th announced promotion to fill Diane Sawyer’s gig in early September. Muir has been guest hosting ABC’s nightly news broadcast all week.

Earlier today when news of the jetliner disaster first broke, it was Muir who appeared on screen when ABC News broke into The View with a special david muir abc newsreport. That special report actually announced that George Stephanopoulos would be anchoring but it was Muir on screen. Sources tell me that though the GMA co-host was announced last month as ABC News’s Chief Anchor for all breaking news broadcasts and specials, the on-air announcement error occurred because news was breaking so quickly and Muir was in the building prepping to host World News tonight. Having already left the studio after GMA wrapped and before the Malaysia Airlines incident broke, Stephanopoulos returned later to take over the coverage for the network. “Our entire team is assembling here. My partner George Stephanopoulos will join us with the coverage here shortly. And of course we’ll be back on with breaking news and a complete report on World News. Stay tuned right here on ABC News. We’ll be right back,” said Muir handing over the report to Stephanopoulos, who came on at 12:08 PM ET.