The flight path from Taipei, Taiwan, to Tianjin, China, does not go directly to Tianjin in a straight line.

Instead, it heads directly north, then banks left (west) before heading north again.

(Flight CCA188, source: FlightAware)

Route: PIANO L3 VIOLA R596 OKATO W13 PINOT B221 OKTUG W506 HGH W554 DOGVI A470 PIX A593 VYK VYK9A/16R (source VatAware)

Does anyone know why this is?