From FlyerGuide Wiki

Platinum: For members who fly 20,000 miles on BWIA during a calendar year. Benefits include:

• 10% mileage bonus on BWIA.
• 5,000-mile bonus.
• Complimentary positive-space upgrades on full, unrestricted coach fares.
• Preferential check-in and priority boarding.
• Unique member credentials.
• Expedited award delivery free of charge.
• Waiver of date change penalty and re-deposit fee on award tickets.

Platinum Preferred: For members who fly 40,000 miles on BWIA during a calendar year. Benefits include the above listed, plus:

• 100% mileage bonus on BWIA.
• 5,000-mile bonus upon flying 80,000 miles on BWIA in one calendar year.
• Capacity-free awards on BWIA at standard award levels.
• Four positive-space upgrades for use on any fare.
• Six additional positive-space upgrades for use on any fare upon flying 80,000 miles in a calendar year.