Why Cellphones Cannot Be Used on Planes

Monday June 10, 2024

Cell phones are an essential part of our everyday lives, but when it comes to air travel, passengers are often reminded to turn off their devices or switch them to airplane mode. Contrary to popular belief, the real reason behind these restrictions has little to do with interfering with the aircraft’s systems. Instead, the main concern historically involved network overload issues with old analog cell phones. Modern digital phones have largely mitigated these issues, but regulatory reasons still justify many of the current restrictions. Additionally, these restrictions are primarily enforced by the FCC, not the FAA, and apply to all flying machines, including gliders, hot air balloons, even free-falling skydivers. In this blog post, we will unravel the true reasons behind the cell phone regulations on airplanes, exploring the technological and regulatory factors at play.

Constant Bombardment with Cellular Signals

Airplanes flying at typical cruising altitudes are constantly bombarded with cellular signals from ground-based cell towers. Understanding the range of cellular devices and towers, along with the altitude at which aircraft operate, helps explain why these signals remain a concern.

  1. Range of a Cellular Device:
    • Typical Range: A cell phone typically has a transmission range of 1-2 kilometers in urban areas, extending up to 10-15 kilometers in rural areas under ideal conditions. - Ideal Conditions: With line-of-sight and no obstructions, a cell phone can potentially transmit up to 30-50 kilometers (18-31 miles).
  2. Range of a Cellular Tower:
    • Typical Range: Cell towers have a range of 1-2 kilometers in urban areas, extending up to 30-50 kilometers (18-31 miles) in rural areas. - Ideal Conditions: Under perfect line-of-sight conditions, cell towers can potentially transmit up to 70-100 kilometers (43-62 miles).
  3. Height of Aircraft Flying:

Given these ranges, it is evident that aircraft at cruising altitudes fly well within the practical transmission limits of both cellular devices and cell towers. While the maximum range of cellular devices and towers are theoretical, aircraft remain in range to receive these signals due to their altitude.

Additionally, while cell towers use directional antennas aimed at the surrounding terrain to optimize coverage and minimize interference, cell phones are inherently omnidirectional. This means that a cell phone signal spreads out in all directions, increasing the likelihood of connecting with multiple cell towers simultaneously, particularly at high altitudes where the line-of-sight to multiple towers is unobstructed.

The Evolution of Regulations

Early regulations were based on concerns that analog cell phones could interfere with cellular networks by simultaneously communicating with multiple ground towers at high speeds and altitudes. This created technical challenges for cellular providers, leading to the Federal Communications Commission (FCC) enacting rules to prevent such issues.

Actual Concerns with Analog Phones

Zack Morris and his phone, via Peter Engel Productions
Zack Morris and his phone, via Peter Engel Productions

Analog cell phones, such as the old-style bag phones or the famous “Zack Morris phone,” operated on a different technology compared to modern digital phones. Analog phones used frequency modulation (FM) to transmit voice signals. Each call was assigned a specific frequency within a band, and the phone maintained that frequency for the duration of the call. Here are the key aspects that caused issues:

  1. Continuous Signal Transmission: Analog phones transmitted a continuous signal that did not switch frequencies dynamically. This meant that as a plane moved through the air, the phone would attempt to communicate with multiple cell towers simultaneously, often without releasing the previous connection. This continuous signal transmission could overload the cellular network on the ground, as multiple towers tried to handle the same call.

  2. Limited Handoff Capability: Unlike modern digital phones, which can seamlessly hand off calls between towers (a process known as “handoff”), analog phones had limited capability to manage these transitions smoothly. The handoff process in analog systems was less efficient, leading to dropped calls or multiple towers attempting to handle the same call. This inefficiency could lead to significant strain on the network, especially in densely populated areas with many cell towers.

  3. Signal Interference: The analog signal was more prone to interference and degradation over long distances. As an aircraft travels at high altitudes and speeds, the analog signal could degrade, causing poor call quality and increased attempts by the phone to reconnect, further straining the network.

  4. Broad Signal Footprint: Analog signals had a broad footprint, meaning they could cover a wide area and potentially interfere with other communications. This was particularly problematic at higher altitudes, where the signal could reach multiple towers spread over a large geographic area.

Modern Digital Phones Modern digital phones use technologies

like Code Division Multiple Access (CDMA) and Global System for Mobile Communications (GSM), which offer several advantages over analog systems:

  1. Dynamic Frequency Management: Digital phones dynamically manage frequency usage, switching channels as needed to maintain call quality and reduce interference. This allows for more efficient use of the available spectrum and minimizes the risk of network overload.

  2. Efficient Handoff: Digital systems have advanced handoff mechanisms that allow seamless transitions between cell towers. This ensures that as an aircraft moves, the phone can maintain a stable connection without causing strain on the network.

  3. Compression and Error Correction: Digital signals are compressed and include error correction, which improves call quality and reduces the risk of dropped calls. This also means that digital phones require less bandwidth, allowing more simultaneous connections without overloading the network.

  4. Controlled Transmission Power: Digital phones adjust their transmission power based on the signal strength and proximity to the cell tower. This reduces unnecessary interference and helps maintain a stable connection, even at high altitudes.

Despite these advancements, the FCC’s regulations still prohibit the use of cellular phones while airborne to avoid any potential disruption to ground-based networks.

FCC Regulations

The FCC enforces these restrictions to protect the integrity of cellular networks. The regulation, specifically 47 CFR § 22.925, states:

47 CFR § 22.925 - Prohibition on airborne operation of cellular telephones > > Cellular telephones installed in or carried aboard airplanes, balloons, or any other type of aircraft must not be operated while such aircraft are airborne (not touching the ground). When any aircraft leaves the ground, all cellular telephones on board that aircraft must be turned off. The following notice must be posted on or near each cellular telephone installed in any aircraft: > > “The use of cellular telephones while this aircraft is airborne is prohibited by FCC rules, and the violation of this rule could result in suspension of service and/or a fine. The use of cellular telephones while this aircraft is on the ground is subject to FAA regulations.”

This regulation helps ensure that network performance is not compromised, a concern that applies to various types of aircraft, including gliders and hot air balloons.

To address the demand for connectivity, airlines have developed in-flight Wi-Fi services that use controlled environments, such as picocells and satellite connections, to provide internet access without relying on ground-based towers. This allows passengers to stay connected without risking network disruption.

Future Outlook

As technology continues to advance, there may be potential changes to current policies. Future solutions could address both technical concerns, allowing for more flexible use of mobile devices during flights. However, for now, the balance between ensuring safety and maintaining network integrity remains a priority.

While technology has reduced some risks associated with cell phone use on airplanes, technical reasons still justify many of the current regulations. These restrictions, enforced by the FCC and applicable to all flying machines, help maintain network integrity and ensure a pleasant flight experience for everyone. We encourage readers to share their opinions and experiences on this topic.