Mass call event

A mass call event or mass calling event (also MCE in telephony usage) is a situation in which an extraordinarily high number of telephone calls are attempted into or out of an area, causing tremendous network congestion, and therefore service which is either significantly degraded or potentially almost completely unavailable.

The term is typically used with mobile telephony systems, in which there are simply not enough radio channels available in a given cell or cells. This causes blocked calls or dropped calls. However, it can also apply to landline phones, in which not enough trunking telephone circuits are available into and out of any given telephone exchange or equivalent switching office at any level of the public switched telephone network (PSTN).

An MCE is typically caused by a sudden disaster of some sort, such as an earthquake or explosion. The 1963 Kennedy assassination represented a mass call event for Washington, DC. A more recent example was the 2013 Boston Marathon bombing, in which mobile network service was so degraded by people checking on the safety of friends and family (or reporting their own status to others) that journalists and the public both assumed that the networks had been shut down to prevent further remote detonations, although this was not the case with any mobile phone company.

...
Wikipedia