I may be missing something, but this seems like a very misleading headline.

The actual article states that the plane "dropped 5,000 feet (1,500m)" and later that the "twinjet descended 1,500m or even lower". This simply means that the plane descended by a relatively small amount compared to 35,000 - 40,000 foot cruising altitudes, not that it was skimming the ground at 5,000 feet.