This looks very, very bad. Ukrainian officials say that a Malaysia Air commercial flight traveling near the Russian border has been shot down, with 295 people on board:

No other source has confirmed that the flight, which left Amsterdam earlier, was shot down as opposed to crashed for some other reason. Sky News reports that Malaysia Air has confirmed an “incident” in the area, though, so the crash itself appears to be real. It would be the second major crash for the airline this year, and this one might touch off a lot more than a so-far futile hemispheric search.

On Twitter, people were recalling the tensions following the KAL 007 shoot-down in 1983:

Reuters has more on this now:

The Boeing plane was flying from Amsterdam to Kuala Lumpur, it said. Reuters could not immediately confirm the report.

The Interfax report said the plane came down 50 km (20 miles) short of entering Russian airspace. It “began to drop, afterwards it was found burning on the ground on Ukrainian territory,” the unnamed source said.

The plane appeared to have come down in a region of military action where Ukrainian government forces are battling pro-Russian separatists.

If this plane was shot down, this would mean an enormous escalation in the Ukraine-Russia crisis. It’s difficult to believe that either Ukraine or Russia would mistake a commercial flight at 10,000 meters, as Reuters reports it, as a hostile military flight — although that was the explanation offered for the KAL 007 shootdown and the US Navy’s shootdown of an Iranian commercial flight in the 1980s as well.  CNN’s expert wonders whether Malaysia Air’s communications got screwed up again and ended up flashing something other than its proper ID, but it seems a little more likely that if it got shot down — still not yet established — it would have been from forces not used to dealing with the distinction between the various kinds of flights.

Ukraine says that the missile was fired by separatists:

Assuming that it was shot down, of course, that would reflect back on Russia, which is supporting the separatists. CNN is now reporting that the Pentagon thinks that’s what happened on an earlier shootdown [corrected]:

CBS has live video coverage:

Obama has now been advised, according to both CBS and The Hill:

Update: Seems that Ukrainian separatists were bragging about taking a plane down about an hour before Malaysia Air plane went down:

If nothing else went missing, that may be a big hint.

Update: Ukraine says its military took no action on any aerial targets today:

That makes sense, as the pro-Russian separatists don’t have many air assets, if any at all. The rebels, though, have been firing on Ukrainian military aircraft, downing two this week.

And more:

Update: Good Lord — the debris field is seven miles wide, which certainly makes it more likely that it exploded in the air:

Update: CBS talked with “Sully” Sullenberger, who wondered why commercial flights took routes over Ukraine at all. The FAA has reminded people that they ordered US carriers months ago to avoid the region for overflights. It looks like other airlines have gotten the message today:

Update: The AP reports that a Buk missile system was seen in the area earlier today:

The Donetsk region government said Thursday’s plane crashed near a village called Grabovo, which it said is currently under the control of armed pro-Russian separatists. The region where the flight was lost has seen severe fighting between Ukrainian forces and pro-Russia separatist rebels in recent days.

A launcher similar to the Buk missile system was seen by Associated Press journalists near the eastern Ukrainian town of Snizhne earlier Thursday.

On Wednesday evening, a Ukrainian fighter jet was shot down by an air-to-air missile from a Russian plane, Ukrainian authorities said Thursday, adding to what Kiev says is mounting evidence that Moscow is directly supporting the separatist insurgents in eastern Ukraine. Security Council spokesman Andrei Lysenko said the pilot of the Sukhoi-25 jet hit by the air-to-air missile was forced to bail after his jet was shot down.

Pro-Russia rebels, meanwhile, claimed responsibility for strikes Wednesday on two Ukrainian Sukhoi-25 jets. The Ukrainian Defense Ministry said the second jet was hit by a portable surface-to-air missile, but added the pilot was unscathed and managed to land his plane safely

Moscow denies Western charges that is supporting the separatists or sowing unrest in its neighbor. The Russian Defense Ministry couldn’t be reached for comment Thursday about the Ukrainian jet and Russia’s foreign ministry didn’t respond to multiple requests for comment.