  We consider the maximal U(3) horizontal scheme as a handle on fermion masses
and mixings. In particular, we attempt to explain the large top Yukawa coupling
and the masses and mixing in the two heaviest generations. A simple model is
constructed by enlarging the matter content of the Standard Model with that of
a $10+\bar{10}$ pair of SU(5). The third generation particles get their masses
when U(3) is broken to U(2). Top quark mass is naturally of order one. Bottom
and tau masses are suppressed because of a hierarchy in the effective Yukawa
couplings and not from the hierarchy in the Higgs doublet vacuum expectation
values. The hierarchy is a consequence of the fact that the particle spectrum
contains an incomplete vector-like generation and can come from hierarchies
between scales of breaking of different grand unified groups. Hierarchies and
mixings between the second and third generation are obtained by introducing a
single parameter epsilon' representing the breaking U(2) -> U(1). As a
consequence, we show that the successful (and previosuly obtained) relations
V_{cb} \approx (m_s / m_b) \approx \sqrt (m_c / m_t) easily follow from our
scheme.
