ABOARD LIAONING AIRCRAFT CARRIER -?A naval formation consisting of aircraft carrier Liaoning has conducted take-off and landing drills in the South China Sea on Monday, a military source said on Tuesday.

The formation, which is on a "cross-sea area" training exercise, involved J-15 fighter jets, as well as several ship-borne helicopters, the source said without giving specific numbers.

Complex hydrological and meteorological conditions in the South China Sea as well as a cold front in area have posed some challenges, but the source said the drill provided important experience in the build-up of combat capability of the aircraft carrier formation.