Thaw lobster tails, if frozen. In a large saucepan, cook lobster tails, uncovered, in enough salted boiling water to cover for 7 to 10 minutes or until shells turn bright red and meat is just tender; drain. To stop the cooking process, rinse with cold water; drain. When cool enough to handle, remove and discard shells. Coarsely chop meat.

In a medium bowl, combine lobster meat, celery, mayonnaise, and lemon juice. Cover; chill for 1 hour.

Just before serving, in a medium skillet, cook pancetta until browned. Drain on paper towels. To serve, line the bottom of each baguette with a butterhead lettuce leaf; spoon lobster mixture on top of lettuce leaf. Place pancetta on lobster mixture. Top each with other half of baguette. Serve immediately. Makes 4 servings.