There have been several Fleet VASSAL modules created by the Fleet community of players. So you'd think VASSAL would be the preferred method for remote game play. But all the modules we've seen include additions and updates that muddy the original designs, sometimes updating the combat factors on the units in the name of realism, or creating additional fog of war that was not in the original design.
We've seen six modules for Sixth Fleet (including a very nice re-make called Mediterranean Fleets), none of which use a scan of the original map. Simultaneous allocation of Strategic Air missions is not provided for in these VASSAL modules.
So rather than sift through these modules making sure two prospective players are playing the same game, what about moving game-play to another medium, and finding a method for true simultaneous assignment of air missions?
Here's a method using Play-by-ACTS and simultaneous emails for strategic air allocations.
Each player must have an account on the Automated Card Tracking System (ACTS) website and an email client with delayed sending capability, such as gmail (called Schedule Send).
Victory Games Sixth Fleet rules, maps, and counters as originally published + official errata of 1 September 1986.
Game play proceeds by text messaging in the ACTS Generic Module, which serves as an online journal of all game activities and die rolls. The ACTS journal is the official record of the game.
The sole exception to using ACTS is the Strategic Air Phase Allocation Segment of each AM turn, which is accomplished by simultaneous email exchange using the delayed send ability of each player's email client.
In each Allocation Segment, players agree on an exact time that allocation emails will be sent. Then each player writes an email detailing his air missions, and specifies that it be sent at the agreed time (so that both emails are sent simultaneously). If a player misses the deadline, he has no strategic air missions for the current game-turn.
Each player may keep track of the state of the board by whatever method desired - using the physical maps and counters or a computerized representation of them. The original game components take precedence over digital representations that may have modified combat factors.
8.1 CAP assignment is not simultaneous: Red player goes first, then Green. This is not explicitly stated in 6th Fleet but is specified in 2nd Fleet.