In 1971 VR-30 joined the Jet Age with two North American CT-39 Saberliners for high-speed executive airlift. In May 1973 the squadron received the first of four C-9B Skytrain II's to further improve its logistics support capability.
Vertical ridges can also be caused by nail injury and certain diseases, including rheumatoid arthritis, according to Rich. If, instead of a series of ridges, there's a single vertical streak, cautions Krant, this could be a sign of a tumor growing at the root of the nail.
Types of Ridging. Disruptions in the deeper layers of the nail bed cause problems such as fingernail ridges. Disruption of the superficial layer creates surface problems such as pitting. Nails grow around 1 milllimeter every six to 10 days, so ridges can indicate when a deficiency began.