China sent warplanes across the Taiwan Strait's median line this morning alongside its navy ships, a negative sign for cross-strait stability as Beijing keeps up military pressure on Taiwan.

• Taiwan's defense ministry tracked 19 Chinese aircraft heading out to sea starting mid-morning, and 15 of them crossed the median line into airspace southwest and central of Taiwan.
• The mix included J-11 and J-16 fighters, JH-7 fighter-bombers, H-6K bombers, KJ-500 early-warning planes, Y-8 electronic jamming aircraft, and drones.
• The planes worked together with Chinese warships under what Beijing calls a "joint combat readiness patrol," which Taiwan describes as harassment of its surrounding air and sea space.
• Taiwan's military tracked the activity with joint intelligence and surveillance and sent up its own aircraft, ships, and shore-based missile systems in response.

Outlook: These joint air-and-sea patrols have become a regular pattern, so expect more crossings of the median line as China keeps testing Taiwan's defenses.