However , most mobile phone networks operate close to capacity during normal times , and spikes in call volumes caused by widespread emergencies often overload the system just when it is needed the most . Examples reported in the media where this has occurred include the September 11 , 2001 attacks , the 2003 Northeast blackouts , the 2005 London Tube bombings , Hurricane Katrina , the 2006 Kiholo Bay earthquake , and the 2007 Minnesota bridge collapse
September 11 , 2001 attacks
September 11 attacks
Mobile telephony