Jim Cramer's Mad Money In-depth Stock Picks 4/21

Includes: AIR, GD, PPDI, RCL

Stocks discussed in the in-depth session of Jim Cramer’s Mad Money TV program, Friday April 21th. Click on a stock ticker for more analysis:

General Dynamics Corp. (NYSE:GD) -- The best play on possible military threats from China, as well as the ongoing Iraq conflict; China is building a massive submarine fleet that the US will need to defend against, and General Dynamics builds a key 'sub killer'; also make Gulf Stream jets that are increasingly popular

Pharmaceutical Product Development Inc. (NASDAQ:PPDI) -- A 'best of breed clinical trial company' that is 'as safe as a copper company'. They do phase 1 through 3 testing as well as data crunching and some investment in promising drugs.

AAR Corp (NYSE:AIR) -- Tighter FAA regulations on planes is bad news for the airlines, but good news for airline maintenance and repair companies such as AAR. Also have big Chinese presence, and the Chinese will need their services as they are repairing, rather than replacing, airplane parts. Another plus: No union problems, as the company isn't unionized.

Executive Interview: Adam Goldstein, President of Royal Caribbean (NYSE:RCL) addressed his company's recent strong earnings report. Cramer attempted to cool his enthusiasm by noting that Carnival (NYSE:CCL) said business in the Carribean isn't so strong, but Goldstein didn't agree with Carnival's assessment. Cramer wasn't entirely convinced.