Communication & internet blackout

Modern communication infrastructure looks more robust than it is. Submarine cables carrying 97–98% of intercontinental internet traffic are physical objects running along specific paths on the ocean floor. Cell towers have battery backups measured in hours, not days. Government-ordered internet shutdowns have increased nearly 280% globally since 2016, from 78 incidents to 296 in 2024 across 51 countries. A comms blackout is not a theoretical scenario — it is a documented, recurring event with multiple distinct causes, each of which shuts networks down differently and for different durations.

This page is distinct from electromagnetic pulse (EMP) and grid-down scenarios. A blackout doesn't require an attack or a catastrophic grid failure. It can result from a solar storm, a dredging ship dragging its anchor across a fiber cable, a power grid region going dark, or a deliberate government decision. Knowing the cause matters because it determines how long the outage lasts, which backup paths stay functional, and what you can do about it.

How blackouts develop by cause

Solar storms and coronal mass ejections (CMEs)

The 1859 Carrington Event set telegraph equipment on fire across North America and Europe via geomagnetically induced currents. A Carrington-magnitude storm today would damage satellite systems, GPS, and high-frequency (HF) radio propagation simultaneously. The 2003 Halloween solar storms caused a 30-minute blackout of HF radio transmissions across Europe, Africa, and Asia.

CMEs travel from the sun to Earth in 18 to 72 hours after a major flare is observed. National Oceanic and Atmospheric Administration (NOAA)'s Space Weather Prediction Center issues alerts when significant events are detected, giving a preparation window. What a CME degrades first: GPS accuracy, HF radio on affected bands, and satellite uplinks. What it does not immediately destroy: ground-based fiber, local mesh radio networks operating on VHF/UHF, and battery-powered AM/FM receivers.

Undersea cable cuts

In March 2024, four undersea cables in the Red Sea were severed, disrupting an estimated 25% of telecommunications traffic between Asia, Europe, and Africa and affecting internet services for more than 100 million people. Undersea cables are cut 100 to 200 times per year globally — the vast majority by ship anchors and fishing equipment rather than sabotage. Repair takes days to months depending on location and available repair ships. Routes with no redundant path go dark until the cable is fixed.

For most US users, cable cuts do not produce a total blackout because multiple redundant transatlantic and transpacific cables exist. Regional exceptions apply: isolated islands, coastal communities served by a single cable landing point, and regions where all cables converge at a geographic chokepoint.

Cascading infrastructure failure

Cell towers and internet exchange points depend on grid power. When the grid fails, backup systems activate — and then run out.

A typical cell tower has lead-acid battery backup sized for 4 to 8 hours at full load. Some towers use larger lithium systems rated for 8 to 24 hours. Towers at critical sites (near hospitals, emergency services) may have diesel generators that run for 72 hours or more if fueled. The FCC guidelines suggest 8 hours minimum for cell sites and 24 hours for central switching offices, but fewer than 30% of US cell sites are adequately protected against a grid outage.

Backhaul is the part most people overlook. Even a tower with a working generator needs a functional fiber or microwave link back to the carrier's core network. If that backhaul or the core network's data center has lost power, the tower is an island — it broadcasts to phones but cannot route calls or data anywhere.

The typical cascade timeline in a regional grid-down event: - Hour 0–4: Most cell towers operational on battery backup - Hour 4–8: Towers without generators begin dropping off - Hour 8–24: Coverage becomes patchy; urban towers with generators survive longer - Beyond 24 hours: Only generator-equipped towers remain; they require fuel resupply

Government-ordered shutdowns

India has conducted 855 documented internet shutdown incidents — more than any other country. Myanmar has 149, and multiple other countries use shutdowns routinely during elections, conflicts, and civil unrest. These shutdowns typically target mobile data and social media first, while voice calls and SMS often remain functional initially. VoIP services go down with data; traditional landline calls sometimes survive longer because they route through older switching infrastructure less dependent on internet connectivity.

In a government-ordered shutdown, shortwave radio and satellite terminals are the only communication paths that bypass domestic internet infrastructure entirely.

Voice calls outlast data in most shutdowns

When mobile data disappears, do not assume voice calls are also gone. Test a standard voice call immediately. SMS messages often continue to route even when data is blocked, because they use a separate signaling channel. Your first action when data drops is to confirm whether voice and SMS are still functional before switching to backup comms.

Offline information strategies

The most dangerous aspect of a comms blackout is losing access to the information you were relying on the internet to provide: maps, medical references, contacts, weather, and news.

Before any outage:

  • Download offline maps for your region. Apps such as Organic Maps and OSMAnd store full vector maps on your device. A downloaded regional map at detail level 13 covers a metropolitan area in around 300 to 500 MB of storage.
  • Print your critical contacts list. If your phone is dead or a blackout has made SMS unreliable, a laminated card in your go-bag is more reliable than any app.
  • Store your medical reference, your household's prescription information, and your emergency plan in printed form.
  • Download weather forecast data when internet is available. A downloaded 7-day forecast gives you a window even after connectivity drops.

During an outage:

  • NOAA Weather Radio broadcasts continuously on seven frequencies: 162.400, 162.425, 162.450, 162.475, 162.500, 162.525, and 162.550 MHz. A basic weather radio receiver costs less than a tank of gas and runs on AA batteries. The network covers approximately 90% of the US population. This is the single most useful one-way information source during any blackout.
  • AM radio stations with backup generators continue broadcasting during grid outages. A battery-powered or hand-crank AM/FM/NOAA receiver keeps you connected to emergency broadcasts at minimal investment.

Communications fallbacks by tier

Tier 1 — Last to fail: licensed radio

Amateur (HAM) radio on HF bands (3–30 MHz) can cover hundreds to thousands of miles independent of any infrastructure, using the ionosphere for propagation. A solar storm can disrupt HF propagation on affected bands, but the network itself is distributed and has no single point of failure. A HAM radio license (Technician class is a one-exam entry point) opens up HF and VHF/UHF capabilities. HAM operators run volunteer emergency nets that activate within hours of a regional event.

GMRS (General Mobile Radio Service) covers local communication out to 5 to 25 miles (8 to 40 km) depending on terrain and antenna, with no infrastructure dependency. A single FCC license covers your entire household. See GMRS for setup guidance.

Tier 2 — Local, no infrastructure: mesh networks

LoRa-based mesh devices (Meshtastic-compatible hardware) communicate peer-to-peer without any internet or cell infrastructure. Range varies by environment: 5 to 15 miles (8 to 24 km) in open terrain, 1 to 3 miles (1.6 to 5 km) in suburban areas, and 0.3 to 1 mile (0.5 to 1.6 km) in dense urban environments. These work during a total infrastructure failure as long as batteries hold. See mesh networking for deployment guidance.

Tier 3 — Satellite: bypasses local infrastructure

Satellite messengers (Garmin inReach, SPOT) and satellite phones operate on orbital networks entirely separate from ground infrastructure. They survive grid outages and government shutdowns of terrestrial networks. They do not survive a CME that disables satellite systems — but that scenario is far rarer than the other blackout types. Satellite terminal costs represent a significant investment; for most households, a reliable radio stack is a better first layer.

Field note

The most overlooked preparation is a laminated two-page reference card: your ten most important contacts by name and phone number, your household's rally point and backup rally point, and the NOAA weather radio frequency for your region. Keep one in your go-bag and one taped inside a kitchen cabinet. No battery required.

Preparation priorities

The right preparation depends on which blackout type you're most likely to face. A suburban household in a tornado-prone area has different exposure than an off-grid property in a region with a history of CME disruption.

For all households, the baseline is: - NOAA weather radio receiver with battery operation and alert tones enabled - Offline maps downloaded on at least one device - Printed critical contacts list - Battery-powered or hand-crank AM/FM radio

For extended outage scenarios (grid-down, major storm, or wildfire): - GMRS handhelds for local household and neighborhood communication - A pre-arranged check-in schedule with your out-of-area contact (call or text at a set time; if no contact after 48 hours, activate your rally point plan)

For regional or national-scale scenarios (CME, government action, infrastructure attack): - HAM radio capability on HF for reaching outside your local area - Physical copies of all critical documentation

Blackout readiness checklist

  • Buy a NOAA weather radio receiver with battery backup and SAME alert tone capability
  • Download offline maps covering your region and two alternative evacuation routes
  • Print and laminate a contact list; store one copy in your go-bag, one at home
  • Program NOAA weather frequencies (162.400–162.550 MHz) into any handheld radio you own
  • Establish a check-in protocol with an out-of-area contact: time, method, fallback
  • If you own GMRS radios, confirm all household members know the primary channel and backup channel
  • Review the grid-down page for power backup guidance — cell towers and your own devices both need power to run