when will build a bridge across the gilbralter straight or the one going to sicily from mainland italy?

Answer 1

When someone installs a sky hook to support them
The Gibraltar Strait is 9 miles and a bridge would be over a major waterway in international waters. And the strait is 600 m deep which makes life exciting for a bridge.
http://clima.casaccia.enea.it/staff/sannino/Papers/JGR_1/Numerical%20modeling%20of%20the%20mean%20exchange%20through%20the%20Strait%20of%20Gibraltar_file/Figures%20-%202001JC000929_file/2001jc000929-o11.gif
Italy-Sicily is about 2 miles across and only 90 meters deep at the sill, but the current is bad
"Although tidal displacements are very small in the Mediterranean Sea (of order of 10 cm), large gradients of tidal displacements are encountered in the Strait of Messina, because the predominantly semidiurnal tides north and south of the strait are approximately in phase opposition. Due to this phase opposition and due to topographic constrictions, the current velocities can attain values as high as 3.0 m/s in the sill region "
3 m/s is 4800 m/hr or 4.8 km/h which is vicious for building and it changes direction twice a day.
http://www.ifm.uni-hamburg.de/ers-sar/Sdata/oceanic/intwaves/messina/intro/index.html

Answer 2

"Il Ponte di Messina" ("Messina Bridge") is actually slated to be built. When new govern was elected last year, it seems all been put on a hyatus, anyway. There are concern about total cost of the work and concern about crime getting involved in it. If they don't hurry, fianancila aid from UE will be lost. And the the frims which undertook the contract will claim for a billionaire indemnification.