Volcanic ash advisories were issued reaching FL500 (Flight level 500) which equals approximately 50,000 feet, and is rare for any volcano for such a large blast to occur.

In Kilometers, this measures at a 15km high blast.

http://ift.tt/1E3WY2b

Bezymianny eruption 2017-12-20 03:55 UTC (local time December 20 15:55). Height of ash plume ~ 15 km ASL extending to the N-E. The webcam is located in seismic station, approximately 7 km (4.3 mi) East of Bezymianny volcano. Please to make reference to Kamchatka Branch of the Geophysical Survey RAS (http://emsd.ru/) if used video.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:
20171220/0447Z
(3) Volcano:
Bezymianny (CAVW #300250)
(4) Current aviation colour code:
RED
(5) Previous aviation colour code:
red
(6) Source:
KVERT
(7) Notice Number:
2017-269
(8) Volcano Location:
N 55 deg 58 min E 160 deg 35 min
(9) Area:
Kamchatka, Russia
(10) Summit Elevation:
9452.96 ft (2882 m)
(11) Volcanic Activity Summary:
According to satellite data by KVERT, ash plume on the height about 15 km a.s.l. drift for about 85 km to the north-east from the volcano.

Strong ash explosions up to 49,200 ft (15 km) a.s.l. occur at this time. Ongoing activity could affect international and low-flying aircraft.
(12) Volcanic cloud height:
49200 ft (15000 m) AMSL Time and method of ash plume/cloud height determination: 20171220/0420Z – Himawari-8
(13) Other volcanic cloud information:
Distance of ash plume/cloud of the volcano: 53 mi (85 km)
Direction of drift of ash plume/cloud of the volcano: NE / azimuth 53 deg
Time and method of ash plume/cloud determination: 20171220/0420Z – Himawari-8
Start time of explosion and how determined: 20171220/0341Z – Video data
(14) Remarks:

(15) Contacts:
Anton A. Nuzhdaev, IVS FEB RAS
envi@kscnet.ru

Duty scientist: +79622825253
(16) Next Notice:
A new VONA will be issued if conditions change significantly or the colour code is changed. VONAs are posted at http://ift.tt/1E3WY2b.