Mexicana de Aviación the world's fourth oldest airline operating under the same name, after the Netherlands's KLM, Colombia's Avianca and Australia's Qantas. In 2009, the Mexicana group of airlines (including Mexicana Click and Mexicana Link) carried just over 11 million passengers (6.6 million on domestic routes and 4.5 million on international routes), using a fleet of some 110 aircraft. Over the three years prior to folding, the Mexicana group had increased their share of what was a burgeoning domestic market, from around 22% at the beginning of 2007 to somewhere between 28% and 30% for most of their final 12 months. This was
S transform S transform S transform as a time–frequency distribution was developed in 1994 for analyzing geophysics data. In this way, the "S" transform is a generalization of the short-time Fourier transform (STFT), extending the continuous wavelet transform and overcoming some of its disadvantages. For one, modulation sinusoids are fixed with respect to the time axis; this localizes the scalable Gaussian window dilations and translations in "S" transform. Moreover, the "S" transform doesn't have a cross-term problem and yields a better signal clarity than Gabor transform. However, the "S" transform has its own disadvantages: the clarity is worse than Wigner distribution function