A First Look at Starlink In-Flight Performance: An Intercontinental Empirical Study

TL;DR

This empirical study evaluates Starlink's in-flight internet performance over the Baltic Sea and Pacific Ocean, revealing throughput variations with altitude and factors affecting latency, providing insights for aviation connectivity improvements.

Contribution

First comprehensive in-flight performance analysis of Starlink, including measurements and factors influencing throughput and latency during air travel.

Findings

Median downlink throughput of 64 Mbps

Median uplink throughput of 24 Mbps at high altitude

Uplink throughput drops to 20 Mbps during descent

Abstract

Starlink delivers Internet services to users across terrestrial, maritime, and aviation domains. The prior works have studied its performance at fixed sites and in-motion vehicles, while an in-depth analysis of in-flight performance remains absent. With major airlines now offering Starlink Internet onboard, there is a growing need to evaluate and improve its performance for aviation users. This paper addresses this shortcoming by conducting in-flight measurements over the Baltic Sea and the Pacific Ocean. Our measurement results show that a single user device experiences median throughputs of 64 Mbps and 24 Mbps for the downlink and uplink, respectively. The median uplink throughput is approximately 33 Mbps when the aircraft maintains an altitude above 17,000 feet. However, a significant reduction in uplink performance is observed during the aircraft descent phase, with the median throughput dropping to around 20 Mbps at lower altitudes. Round-trip time (RTT) is highly dependent on the location of the ground station being pinged and the use of inter-satellite links (ISLs). We dive deeper into 5.5 hours of ping measurements collected over the Pacific Ocean and investigate factors influencing RTT, hypothesizing that ISLs routing, data queuing at satellites, and feeder link congestion contribute to deviations from theoretical values. For comparative analysis, we evaluate the Starlink ground terminal and in-flight connectivity performance from the perspectives of a residential user and an airline passenger, respectively.