The formation of cis-trans isomers is a consequence of the absence of free rotation. Geometric isomers that only differ from each other in the 3-dimensional arrangement of the substituents in space. They have identical bonding and substituents. Alkane.
What sells out first: Christmas/New Years, Presidents Week in February, Spring Break Week in March, Easter Week and July/August sailings when the children are out of school. To get the space you want on the cruise and necessary air arrangements, don't hesitate to book 9 to 11 months in advance if possible. The remainder of February, March and April sailings usually start to fill up once the weather starts to turn cold in the Northeast and Midwest.
Here are some other interesting findings from CheapAir.com's data: How far to book in advance: Seven weeks for domestic flights. Book 11 to 12 weeks out for international flights. The worst day to buy: Within 11 days of your flight. One day before the flight was the absolute worst. The best fares for Thanksgiving: For Thanksgiving 2012, the best day to buy was, on average, 96 days (about 14 weeks) before the flight. The bottom line: Do your homework before booking any flight, and make sure you've got the right tools to set yourself up for the best fares.