Why Closing Pakistan's Airspace Made Taipei-London Flights Faster

Maps Can Mislead

Taiwanese carriers flying to Europe traditionally used a southern route via Southeast Asia, India, Pakistan, Iran, and Turkey. On a flat Mercator map this looks shorter than the northern route crossing the Sea of Japan and Siberia. However, Earth is a sphere; the shortest path between two points is a great-circle arc that bends toward the pole. Using an azimuthal equidistant projection centered on Taipei shows the northern route is closer to the true great circle.

Calculating spherical distances: the original southern route via Pakistan is about 12,300 km; a detour around Pakistan via the Arabian Sea and Persian Gulf is about 12,900 km; the northern route via Russia is about 11,800 km. These figures match actual flight-tracking data.

Time Depends on Wind, Not Just Distance

Ground speed equals true airspeed minus headwind component. Flight time can be approximated as: time = distance / (airspeed - average headwind) + fixed ground time (takeoff, climb, descent). Using a typical cruise speed of 900 km/h and 1 hour fixed time, the measured CI81 flight data yields an average headwind of ~77 km/h on the southern route versus ~35 km/h on the northern route. In winter, westbound flights on southerly tracks encounter stronger jet-stream headwinds, while the more northerly track avoids the core of the westerlies.

Notably, October 25 marked the start of the IATA winter scheduling season. Aviation outlet One Mile at a Time also noted that winter westbound flights via Russia save roughly an hour. Whether the reroute was driven solely by Pakistan's restriction, seasonal schedule changes, or both remains unclear.

Not Every City Benefits Equally

Applying the same model to several European destinations:

London, Amsterdam: northern route faster by >1 hour

Paris, Frankfurt, Prague: faster by ~30 minutes

Rome: northern route slower by ~30 minutes (actual CI75 added ~1,000 km and 40 minutes)

A dividing line runs roughly through Milan and Vienna. North of this line the northern route wins; south of it the original southern route remains quicker. The simplified model has non-trivial error margins but its directional predictions align with real-world data.

The Cost of Closing a Route

Abstractly, the Taipei-Europe network has multiple paths. Closing one path imposes a cost equal to the difference between the original path's cost and the second-best alternative. If the alternative is nearly as good, the cost approaches zero; if the alternative was already better but unused for other reasons, the cost can be negative (i.e., a gain).

A 2025 contrast: during India-Pakistan tensions, Pakistan closed its airspace for 48 hours. Taiwanese carriers then had no Russian option (voluntarily avoided), forcing a longer southern detour with technical stops in Bangkok and some cancellations. This time, the Russian corridor was available, so most flights simply switched routes — and London flights even arrived earlier.

The same country's airspace closure had vastly different impacts solely because a viable second route existed.

Caveats

The northern route has drawbacks. Since the Russia-Ukraine conflict, EASA has issued risk warnings for parts of Russian airspace. U.S. carriers are prohibited from code-sharing on flights that overfly Russia. Taiwanese carriers avoided Russia for years; aviation media attribute this to voluntary restrictions by Taiwan's CAA, while the CAA denies ever banning such overflights — the author could not verify either claim. Also, the wind analysis uses only one winter dataset; summer jet streams weaken and shift north, potentially altering the conclusion.

Conclusion

The ultimate outcome remains uncertain. But the data shows whether an airspace closure can choke a route depends on Earth's geometry, seasonal winds, and the availability of alternatives. Relying solely on flat maps can overstate or understate the true impact.