Using xsl:for-each for every 2 elements ?

Hi,

Is it possible to use xsl:for-each for every two elements ?

E.g
----------
<data>
  <flights>
   <flt>onward</flt>
   <flt>return</flt>
   <flt>onward</flt>
   <flt>return</flt>
  </flights>

 <availability>
  <avail>N</avail>
  <avail>Y</avail>
  <avail>N</avail>
  <avail>Y</avail>
  </availability>

</data>
--------
The second part of the problem is that, the above have to be
iterated/grouped using a method that would still allow me to somehow
co-relate the first <avail> in <availability> with the first <flt> in
<flights>. That's my second question.. how to co-relate that since
their in the same level of hierarchy  ??

Thanks,

Ahsan